Formation of large-scale structure from cosmic-string loops and cold dark matter

NASA Technical Reports Server (NTRS)

Melott, Adrian L.; Scherrer, Robert J.

1987-01-01

Some results from a numerical simulation of the formation of large-scale structure from cosmic-string loops are presented. It is found that even though G x mu is required to be lower than 2 x 10 to the -6th (where mu is the mass per unit length of the string) to give a low enough autocorrelation amplitude, there is excessive power on smaller scales, so that galaxies would be more dense than observed. The large-scale structure does not include a filamentary or connected appearance and shares with more conventional models based on Gaussian perturbations the lack of cluster-cluster correlation at the mean cluster separation scale as well as excessively small bulk velocities at these scales.

Evaluating the Performance of the Goddard Multi-Scale Modeling Framework against GPM, TRMM and CloudSat/CALIPSO Products

NASA Astrophysics Data System (ADS)

Chern, J. D.; Tao, W. K.; Lang, S. E.; Matsui, T.; Mohr, K. I.

2014-12-01

Four six-month (March-August 2014) experiments with the Goddard Multi-scale Modeling Framework (MMF) were performed to study the impacts of different Goddard one-moment bulk microphysical schemes and large-scale forcings on the performance of the MMF. Recently a new Goddard one-moment bulk microphysics with four-ice classes (cloud ice, snow, graupel, and frozen drops/hail) has been developed based on cloud-resolving model simulations with large-scale forcings from field campaign observations. The new scheme has been successfully implemented to the MMF and two MMF experiments were carried out with this new scheme and the old three-ice classes (cloud ice, snow graupel) scheme. The MMF has global coverage and can rigorously evaluate microphysics performance for different cloud regimes. The results show MMF with the new scheme outperformed the old one. The MMF simulations are also strongly affected by the interaction between large-scale and cloud-scale processes. Two MMF sensitivity experiments with and without nudging large-scale forcings to those of ERA-Interim reanalysis were carried out to study the impacts of large-scale forcings. The model simulated mean and variability of surface precipitation, cloud types, cloud properties such as cloud amount, hydrometeors vertical profiles, and cloud water contents, etc. in different geographic locations and climate regimes are evaluated against GPM, TRMM, CloudSat/CALIPSO satellite observations. The Goddard MMF has also been coupled with the Goddard Satellite Data Simulation Unit (G-SDSU), a system with multi-satellite, multi-sensor, and multi-spectrum satellite simulators. The statistics of MMF simulated radiances and backscattering can be directly compared with satellite observations to assess the strengths and/or deficiencies of MMF simulations and provide guidance on how to improve the MMF and microphysics.

Diagnostic performance of an indirect enzyme-linked immunosorbent assay (ELISA) to detect bovine leukemia virus antibodies in bulk-tank milk samples.

PubMed

Nekouei, Omid; Durocher, Jean; Keefe, Greg

2016-07-01

This study assessed the diagnostic performance of a commercial ELISA for detecting bovine leukemia virus antibodies in bulk-tank milk samples from eastern Canada. Sensitivity and specificity of the test were estimated at 97.2% and 100%, respectively. The test was recommended as a cost-efficient tool for large-scale screening programs.

Diagnostic performance of an indirect enzyme-linked immunosorbent assay (ELISA) to detect bovine leukemia virus antibodies in bulk-tank milk samples

PubMed Central

Nekouei, Omid; Durocher, Jean; Keefe, Greg

2016-01-01

This study assessed the diagnostic performance of a commercial ELISA for detecting bovine leukemia virus antibodies in bulk-tank milk samples from eastern Canada. Sensitivity and specificity of the test were estimated at 97.2% and 100%, respectively. The test was recommended as a cost-efficient tool for large-scale screening programs. PMID:27429469

Cosmic Bulk Flow and the Local Motion from Cosmicflows-2

NASA Astrophysics Data System (ADS)

Courtois, Helene M.; Hoffman, Yehuda; Tully, R. Brent

2015-08-01

Full sky surveys of peculiar velocity are arguably the best way to map the large scale structure out to distances of a few times 100 Mpc/h.Using the largest and most accurate ever catalog of galaxy peculiar velocities Cosmicflows-2, the large scale structure has been reconstructed by means of the Wiener filter and constrained realizations assuming as a Bayesian prior model the LCDM standard model of cosmology. The present paper focuses on studying the bulk flow of the local flow field, defined as the mean velocity of top-hat spheres with radii ranging out to R=500 Mpc/h. Our main results is that the estimated bulk flow is consistent with the LCDM model with the WMAP inferred cosmological parameters. At R=50 (150)Mpc/h the estimated bulk velocity is 250 +/- 21 (239 +/- 38) km/s. The corresponding cosmic variance at these radii is 126 (60) km/s, which implies that these estimated bulk flows are dominated by the data and not by the assumed prior model. The estimated bulk velocity is dominated by the data out to R ˜200 Mpc/h, where the cosmic variance on the individual Supergalactic Cartesian components (of the r.m.s. values) exceeds the variance of the constrined realizations by at least a factor of 2. The SGX and SGY components of the CMB dipole velocity are recovered by the Wiener Filter velocity field down to a very few km/s. The SGZ component of the estimated velocity, the one that is most affected by the Zone of Avoidance, is off by 126km/s (an almost 2 sigma discrepancy).The bulk velocity analysis reported here is virtually unaffected by the Malmquist bias and very similar results are obtained for the data with and without the bias correction.

Superconductor bearings, flywheels and transportation

NASA Astrophysics Data System (ADS)

Werfel, F. N.; Floegel-Delor, U.; Rothfeld, R.; Riedel, T.; Goebel, B.; Wippich, D.; Schirrmeister, P.

2012-01-01

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS-FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

Response of deep and shallow tropical maritime cumuli to large-scale processes

NASA Technical Reports Server (NTRS)

Yanai, M.; Chu, J.-H.; Stark, T. E.; Nitta, T.

1976-01-01

The bulk diagnostic method of Yanai et al. (1973) and a simplified version of the spectral diagnostic method of Nitta (1975) are used for a more quantitative evaluation of the response of various types of cumuliform clouds to large-scale processes, using the same data set in the Marshall Islands area for a 100-day period in 1956. The dependence of the cloud mass flux distribution on radiative cooling, large-scale vertical motion, and evaporation from the sea is examined. It is shown that typical radiative cooling rates in the tropics tend to produce a bimodal distribution of mass spectrum exhibiting deep and shallow clouds. The bimodal distribution is further enhanced when the large-scale vertical motion is upward, and a nearly unimodal distribution of shallow clouds prevails when the relative cooling is compensated by the heating due to the large-scale subsidence. Both deep and shallow clouds are modulated by large-scale disturbances. The primary role of surface evaporation is to maintain the moisture flux at the cloud base.

Spatial confinement of active microtubule networks induces large-scale rotational cytoplasmic flow

PubMed Central

Suzuki, Kazuya; Miyazaki, Makito; Takagi, Jun; Itabashi, Takeshi; Ishiwata, Shin’ichi

2017-01-01

Collective behaviors of motile units through hydrodynamic interactions induce directed fluid flow on a larger length scale than individual units. In cells, active cytoskeletal systems composed of polar filaments and molecular motors drive fluid flow, a process known as cytoplasmic streaming. The motor-driven elongation of microtubule bundles generates turbulent-like flow in purified systems; however, it remains unclear whether and how microtubule bundles induce large-scale directed flow like the cytoplasmic streaming observed in cells. Here, we adopted Xenopus egg extracts as a model system of the cytoplasm and found that microtubule bundle elongation induces directed flow for which the length scale and timescale depend on the existence of geometrical constraints. At the lower activity of dynein, kinesins bundle and slide microtubules, organizing extensile microtubule bundles. In bulk extracts, the extensile bundles connected with each other and formed a random network, and vortex flows with a length scale comparable to the bundle length continually emerged and persisted for 1 min at multiple places. When the extracts were encapsulated in droplets, the extensile bundles pushed the droplet boundary. This pushing force initiated symmetry breaking of the randomly oriented bundle network, leading to bundles aligning into a rotating vortex structure. This vortex induced rotational cytoplasmic flows on the length scale and timescale that were 10- to 100-fold longer than the vortex flows emerging in bulk extracts. Our results suggest that microtubule systems use not only hydrodynamic interactions but also mechanical interactions to induce large-scale temporally stable cytoplasmic flow. PMID:28265076

Efficiency of bulk-heterojunction organic solar cells

PubMed Central

Scharber, M.C.; Sariciftci, N.S.

2013-01-01

During the last years the performance of bulk heterojunction solar cells has been improved significantly. For a large-scale application of this technology further improvements are required. This article reviews the basic working principles and the state of the art device design of bulk heterojunction solar cells. The importance of high power conversion efficiencies for the commercial exploitation is outlined and different efficiency models for bulk heterojunction solar cells are discussed. Assuming state of the art materials and device architectures several models predict power conversion efficiencies in the range of 10–15%. A more general approach assuming device operation close to the Shockley–Queisser-limit leads to even higher efficiencies. Bulk heterojunction devices exhibiting only radiative recombination of charge carriers could be as efficient as ideal inorganic photovoltaic devices. PMID:24302787

Superfluid-like turbulence in cosmology

NASA Technical Reports Server (NTRS)

Gradwohl, Ben-Ami

1991-01-01

A network of vortices in a superfluid system exhibits turbulent behavior. It is argued that the universe may have experienced such a phase of superfluid-like turbulence due to the existence of a coherent state with non-topological charge and a network of global strings. The unique feature of a distribution of turbulent domains is that it can yield non-gravitationally induced large-scale coherent velocities. It may be difficult, however, to relate these velocities to the observed large-scale bulk motion.

Mass production of bulk artificial nacre with excellent mechanical properties.

PubMed

Gao, Huai-Ling; Chen, Si-Ming; Mao, Li-Bo; Song, Zhao-Qiang; Yao, Hong-Bin; Cölfen, Helmut; Luo, Xi-Sheng; Zhang, Fu; Pan, Zhao; Meng, Yu-Feng; Ni, Yong; Yu, Shu-Hong

2017-08-18

Various methods have been exploited to replicate nacre features into artificial structural materials with impressive structural and mechanical similarity. However, it is still very challenging to produce nacre-mimetics in three-dimensional bulk form, especially for further scale-up. Herein, we demonstrate that large-sized, three-dimensional bulk artificial nacre with comprehensive mimicry of the hierarchical structures and the toughening mechanisms of natural nacre can be facilely fabricated via a bottom-up assembly process based on laminating pre-fabricated two-dimensional nacre-mimetic films. By optimizing the hierarchical architecture from molecular level to macroscopic level, the mechanical performance of the artificial nacre is superior to that of natural nacre and many engineering materials. This bottom-up strategy has no size restriction or fundamental barrier for further scale-up, and can be easily extended to other material systems, opening an avenue for mass production of high-performance bulk nacre-mimetic structural materials in an efficient and cost-effective way for practical applications.Artificial materials that replicate the mechanical properties of nacre represent important structural materials, but are difficult to produce in bulk. Here, the authors exploit the bottom-up assembly of 2D nacre-mimetic films to fabricate 3D bulk artificial nacre with an optimized architecture and excellent mechanical properties.

Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America

USGS Publications Warehouse

Hanley, Kevin W.; Wollheim, Wilfred M.; Salisbury, Joseph; Huntington, Thomas G.; Aiken, George R.

2013-01-01

Understanding the processes controlling the transfer and chemical composition of dissolved organic carbon (DOC) in freshwater systems is crucial to understanding the carbon cycle and the effects of DOC on water quality. Previous studies have identified watershed-scale controls on bulk DOC flux and concentration among small basins but fewer studies have explored controls among large basins or simultaneously considered the chemical composition of DOC. Because the chemical character of DOC drives riverine biogeochemical processes such as metabolism and photodegradation, accounting for chemical character in watershed-scale studies will improve the way bulk DOC variability in rivers is interpreted. We analyzed DOC quantity and chemical character near the mouths of 17 large North American rivers, primarily between 2008 and 2010, and identified watershed characteristics that controlled variability. We quantified DOC chemical character using both specific ultraviolet absorbance at 254 nm (SUVA254) and XAD-resin fractionation. Mean DOC concentration ranged from 2.1 to 47 mg C L−1 and mean SUVA254 ranged from 1.3 to 4.7 L mg C−1 m−1. We found a significant positive correlation between basin wetland cover and both bulk DOC concentration (R2 = 0.78; p < 0.0001) and SUVA254 (R2 = 0.91; p < 0.0001), while other land use characteristics were not correlated. The strong wetland relationship with bulk DOC concentration is similar to that found by others in small headwater catchments. However, two watersheds with extremely long surface water residence times, the Colorado and St. Lawrence, diverged from this wetland relationship. These results suggest that the role of riverine processes in altering the terrestrial DOC signal at the annual scale was minimal except in river systems with long surface water residence times. However, synoptic DOC sampling of both quantity and character throughout river networks will be needed to more rigorously test this finding. The inclusion of DOC chemical character will be vital to achieving a more complete understanding of bulk DOC dynamics in large river systems.

Review of Dynamic Modeling and Simulation of Large Scale Belt Conveyor System

NASA Astrophysics Data System (ADS)

He, Qing; Li, Hong

Belt conveyor is one of the most important devices to transport bulk-solid material for long distance. Dynamic analysis is the key to decide whether the design is rational in technique, safe and reliable in running, feasible in economy. It is very important to study dynamic properties, improve efficiency and productivity, guarantee conveyor safe, reliable and stable running. The dynamic researches and applications of large scale belt conveyor are discussed. The main research topics, the state-of-the-art of dynamic researches on belt conveyor are analyzed. The main future works focus on dynamic analysis, modeling and simulation of main components and whole system, nonlinear modeling, simulation and vibration analysis of large scale conveyor system.

Vibration and Thermal Cycling Effects on Bulk-fill Insulation Materials for Cryogenic Tanks

NASA Astrophysics Data System (ADS)

Fesmire, J. E.; Augustynowicz, S. D.; Nagy, Z. F.; Sojourner, S. J.; Morris, D. L.

2006-04-01

Large-scale (1,000,000 liters or more) cryogenic storage tanks are typically perlite-insulated double-walled vessels. Associated problems with perlite, such as mechanical compaction and settling, could be greatly reduced by using newer bulk-fill materials such as glass bubbles or aerogel beads. Using the newer materials should translate to lower life cycle costs and improved system reliability. NASA Kennedy Space Center is leveraging its experience in the areas of materials development, insulation testing, and cryogenic systems design to develop an insulation retrofit option that will meet both industry and NASA requirements. A custom 10-liter dewar test apparatus, developed by the KSC Cryogenics Test Laboratory, was used to determine the vibration and thermal cycling effects on different bulk-fill insulation materials for cryogenic tanks. The testing included liquid-nitrogen boiloff testing and thermal cycling (with vibration) of a number of test dewars. Test results show that glass bubbles have better thermal performance and less mechanical compaction compared to perlite powder. The higher cost of the bulk material should be offset by reduced commodity loss from boiloff and improvements in material handling, evacuation, and vacuum retention. The long-term problem with settling and compaction of perlite should also be eliminated. Aerogel beads are superior for the no-vacuum condition and can now be considered in some applications. Further studies on large-scale systems are presently being pursued.

A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications

NASA Astrophysics Data System (ADS)

Savina, Irina N.; Ingavle, Ganesh C.; Cundy, Andrew B.; Mikhalovsky, Sergey V.

2016-02-01

The development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200 μm in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400 ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications.

High-resolution hybrid simulations of turbulence from inertial to sub-proton scales

NASA Astrophysics Data System (ADS)

Franci, Luca; Hellinger, Petr; Landi, Simone; Matteini, Lorenzo; Verdini, Andrea

2015-04-01

We investigate properties of turbulence from MHD scales to ion scales by means of two-dimensional, large-scale, high-resolution hybrid particle-in-cell simulations, which to our knowledge constitute the most accurate hybrid simulations of ion scale turbulence ever presented so far. We impose an initial ambient magnetic field perpendicular to the simulation box, and we add a spectrum of large-scale, linearly polarized Alfvén waves, balanced and Alfvénically equipartitioned, on average. When turbulence is fully developed, we observe an inertial range which is characterized by the power spectrum of perpendicular magnetic field fluctuations following a Kolmogorov law with spectral index close to -5/3, while the proton bulk velocity fluctuations exhibit a less steeper slope with index close to -3/2. Both these trends hold over a full decade. A definite transition is observed at a scale of the order of the proton inertial length, above which both spectra steepen, with the perpendicular magnetic field still exhibiting a power law with spectral index about -3 over another full decade. The spectrum of perpendicular electric fluctuations follows the one of the proton bulk velocity at MHD scales and reaches a sort of plateau at small scales. The turbulent nature of our data is also supported by the presence of intermittency. This is revealed by the non-Gaussianity of the probability distribution functions of MHD primitive variables increasing as approaching kinetic scales. All these features are in good agreement with solar wind observations.

REVIEWS OF TOPICAL PROBLEMS: The large-scale structure of the universe

NASA Astrophysics Data System (ADS)

Shandarin, S. F.; Doroshkevich, A. G.; Zel'dovich, Ya B.

1983-01-01

A survey is given of theories for the origin of large-scale structure in the universe: clusters and superclusters of galaxies, and vast black regions practically devoid of galaxies. Special attention is paid to the theory of a neutrino-dominated universe—a cosmology in which electron neutrinos with a rest mass of a few tens of electron volts would contribute the bulk of the mean density. The evolution of small perturbations is discussed, and estimates are made for the temperature anisotropy of the microwave background radiation on various angular scales. The nonlinear stage in the evolution of smooth irrotational perturbations in a lowpressure medium is described in detail. Numerical experiments simulating large-scale structure formation processes are discussed, as well as their interpretation in the context of catastrophe theory.

Linux OS Jitter Measurements at Large Node Counts using a BlueGene/L

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Terry R; Tauferner, Mr. Andrew; Inglett, Mr. Todd

2010-01-01

We present experimental results for a coordinated scheduling implementation of the Linux operating system. Results were collected on an IBM Blue Gene/L machine at scales up to 16K nodes. Our results indicate coordinated scheduling was able to provide a dramatic improvement in scaling performance for two applications characterized as bulk synchronous parallel programs.

Cuprous Oxide Scale up: Gram Production via Bulk Synthesis using Classic Solvents at Low Temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, A.; Han, T. Y.

Cuprous oxide is a p-type semiconducting material that has been highly researched for its interesting properties. Many small-scale syntheses have exhibited excellent control over size and morphology. As the demand for cuprous oxide grows, the synthesis method need to evolve to facilitate large-scale production. This paper supplies a facile bulk synthesis method for Cu₂O on average, 1-liter reaction volume can produce 1 gram of particles. In order to study the shape and size control mechanisms on such a scale, the reaction volume was diminished to 250 mL producing on average 0.3 grams of nanoparticles per batch. Well-shaped nanoparticles have beenmore » synthesized using an aqueous solution of CuCl₂, NaOH, SDS surfactant, and NH₂OH-HCl at mild temperatures. The time allotted between the addition of NaOH and NH₂OH-HCl was determined to be critical for Cu(OH)2 production, an important precursor to the final produce The effects of stirring rates on a large scale was also analyzed during reagent addition and post reagent addition. A morphological change from rhombic dodecahedra to spheres occurred as the stirring speed was increased. The effects of NH₂OH-HCl concentration were also studied to control the etching effects of the final product.« less

Large scale EMF in current sheets induced by tearing modes

NASA Astrophysics Data System (ADS)

Mizerski, Krzysztof A.

2018-02-01

An extension of the analysis of resistive instabilities of a sheet pinch from a famous work by Furth et al (1963 Phys. Fluids 6 459) is presented here, to study the mean electromotive force (EMF) generated by the developing instability. In a Cartesian configuration and in the presence of a current sheet first the boundary layer technique is used to obtain global, matched asymptotic solutions for the velocity and magnetic field and then the solutions are used to calculate the large-scale EMF in the system. It is reported, that in the bulk the curl of the mean EMF is linear in {{j}}0\\cdot {{B}}0, a simple pseudo-scalar quantity constructed from the large-scale quantities.

Large-Scale Fabrication of Silicon Nanowires for Solar Energy Applications.

PubMed

Zhang, Bingchang; Jie, Jiansheng; Zhang, Xiujuan; Ou, Xuemei; Zhang, Xiaohong

2017-10-11

The development of silicon (Si) materials during past decades has boosted up the prosperity of the modern semiconductor industry. In comparison with the bulk-Si materials, Si nanowires (SiNWs) possess superior structural, optical, and electrical properties and have attracted increasing attention in solar energy applications. To achieve the practical applications of SiNWs, both large-scale synthesis of SiNWs at low cost and rational design of energy conversion devices with high efficiency are the prerequisite. This review focuses on the recent progresses in large-scale production of SiNWs, as well as the construction of high-efficiency SiNW-based solar energy conversion devices, including photovoltaic devices and photo-electrochemical cells. Finally, the outlook and challenges in this emerging field are presented.

Theory of turbulent thermal convection

NASA Astrophysics Data System (ADS)

Lohse, Detlef

2002-03-01

We review our universal theory for the scaling of the Nusselt number and the Reynolds number as functions of the Rayleigh number and the Prandtl number in turbulent thermal convection (Siegfried Grossmann and Detlef Lohse, J. Fluid Mech. 407, 27 (2000); Phys. Rev. Lett. 86, 3316 (2001)). This theory is based on a decomposition of the energy dissipation and the thermal dissipation into a bulk and a boundary layer contribution. We will in particular focus on the behavior for large Prandtl numbers and on the scaling behavior of the Reynolds number for which new experimental results have been obtained recently. We will also address the chaotic switching of the large scale wind of turbulence.

Exploring the bulk in AdS /CFT : A covariant approach

NASA Astrophysics Data System (ADS)

Engelhardt, Netta

2017-03-01

I propose a general, covariant way of defining when one region is "deeper in the bulk" than another. This definition is formulated outside of an event horizon (or in the absence thereof) in generic geometries; it may be applied to both points and surfaces, and it may be used to compare the depth of bulk points or surfaces relative to a particular boundary subregion or relative to the entire boundary. Using the recently proposed "light-cone cut" formalism, the comparative depth between two bulk points can be determined from the singularity structure of Lorentzian correlators in the dual field theory. I prove that, by this definition, causal wedges of progressively larger regions probe monotonically deeper in the bulk. The definition furthermore matches expectations in pure AdS and in static AdS black holes with isotropic spatial slices, where a well-defined holographic coordinate exists. In terms of holographic renormalization group flow, this new definition of bulk depth makes contact with coarse graining over both large distances and long time scales.

Performance of Sweetpotato for Bioregenerative Life Support

NASA Technical Reports Server (NTRS)

Barta, Daniel J.; Henderson, Keith E.; Mortley, Desmond G.; Henninger, Donald L.

2001-01-01

Sweetpotato was successfully grown to harvest maturity in a large-scale atmospherically-closed controlled environment chamber. Yield of edible biomass and capacity for contributing to air revitalization and water recovery were documented. Yield was slightly less than that found in smaller-scale studies, but this is not unusual (Wheeler 1999). Continued work is suggested to improve control of storage root initiation, bulking and vine growth.

High-order multipole radiation from quantum Hall states in Dirac materials

NASA Astrophysics Data System (ADS)

Gullans, Michael J.; Taylor, Jacob M.; Imamoǧlu, Ataç; Ghaemi, Pouyan; Hafezi, Mohammad

2017-06-01

We investigate the optical response of strongly disordered quantum Hall states in two-dimensional Dirac materials and find qualitatively different effects in the radiation properties of the bulk versus the edge. We show that the far-field radiation from the edge is characterized by large multipole moments (>50 ) due to the efficient transfer of angular momentum from the electrons into the scattered light. The maximum multipole transition moment is a direct measure of the coherence length of the edge states. Accessing these multipole transitions would provide new tools for optical spectroscopy and control of quantum Hall edge states. On the other hand, the far-field radiation from the bulk appears as random dipole emission with spectral properties that vary with the local disorder potential. We determine the conditions under which this bulk radiation can be used to image the disorder landscape. Such optical measurements can probe submicron-length scales over large areas and provide complementary information to scanning probe techniques. Spatially resolving this bulk radiation would serve as a novel probe of the percolation transition near half filling.

Advanced bulk processing of lightweight materials for utilization in the transportation sector

NASA Astrophysics Data System (ADS)

Milner, Justin L.

The overall objective of this research is to develop the microstructure of metallic lightweight materials via multiple advanced processing techniques with potentials for industrial utilization on a large scale to meet the demands of the aerospace and automotive sectors. This work focused on (i) refining the grain structure to increase the strength, (ii) controlling the texture to increase formability and (iii) directly reducing processing/production cost of lightweight material components. Advanced processing is conducted on a bulk scale by several severe plastic deformation techniques including: accumulative roll bonding, isolated shear rolling and friction stir processing to achieve the multiple targets of this research. Development and validation of the processing techniques is achieved through wide-ranging experiments along with detailed mechanical and microstructural examination of the processed material. On a broad level, this research will make advancements in processing of bulk lightweight materials facilitating industrial-scale implementation. Where accumulative roll bonding and isolated shear rolling, currently feasible on an industrial scale, processes bulk sheet materials capable of replacing more expensive grades of alloys and enabling low-temperature and high-strain-rate formability. Furthermore, friction stir processing to manufacture lightweight tubes, made from magnesium alloys, has the potential to increase the utilization of these materials in the automotive and aerospace sectors for high strength - high formability applications. With the increased utilization of these advanced processing techniques will significantly reduce the cost associated with lightweight materials for many applications in the transportation sectors.

125 GeV Higgs boson mass from 5D gauge-Higgs unification

NASA Astrophysics Data System (ADS)

Carson, Jason; Okada, Nobuchika

2018-03-01

In the context of a simple gauge-Higgs unification (GHU) scenario based on the gauge group SU(3)×U(1)^' in a 5D flat space-time, we investigate the possibility of reproducing the observed Higgs boson mass of around 125 GeV. We introduce bulk fermion multiplets with a bulk mass and a (half-)periodic boundary condition. In our analysis, we adopt a low-energy effective theoretical approach of the GHU scenario, where the running Higgs quartic coupling is required to vanish at the compactification scale. Under this "gauge-Higgs condition," we investigate the renormalization group evolution of the Higgs quartic coupling and find a relation between the bulk mass and the compactification scale so as to reproduce the 125 GeV Higgs boson mass. Through quantum corrections at the one-loop level, the bulk fermions contribute to the Higgs boson production and decay processes and deviate the Higgs boson signal strengths at the Large Hadron Collider experiments from the Standard Model (SM) predictions. Employing the current experimental data that show that the Higgs boson signal strengths for a variety of Higgs decay modes are consistent with the SM predictions, we obtain lower mass bounds on the lightest mode of the bulk fermions to be around 1 TeV.

A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications

PubMed Central

Savina, Irina N.; Ingavle, Ganesh C.; Cundy, Andrew B.; Mikhalovsky, Sergey V.

2016-01-01

The development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200 μm in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400 ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications. PMID:26883390

Achieving large linear elasticity and high strength in bulk nanocompsite via synergistic effect

DOE PAGES

Hao, Shijie; Cui, Lishan; Guo, Fangmin; ...

2015-03-09

Elastic strain in bulk metallic materials is usually limited to only a fraction of 1%. Developing bulk metallic materials showing large linear elasticity and high strength has proven to be difficult. Here, based on the synergistic effect between nanowires and orientated martensite NiTi shape memory alloy, we developed an in-situ Nb nanowires-orientated martensitic NiTi matrix composite showing an ultra-large linear elastic strain of 4% and an ultrahigh yield strength of 1.8 GPa. This material also has a high mechanical energy storage efficiency of 96% and a high energy storage density of 36 J/cm 3 that is almost one order ofmore » larger than that of spring steel. It is demonstrated that the synergistic effect allows the exceptional mechanical properties of nanowires to be harvested at macro scale and the mechanical properties of matrix to be greatly improved, resulting in these superior properties. This research provides new avenues for developing advanced composites with superior properties by using effective synergistic effect between components.« less

Chebyshev polynomial filtered subspace iteration in the discontinuous Galerkin method for large-scale electronic structure calculations

DOE PAGES

Banerjee, Amartya S.; Lin, Lin; Hu, Wei; ...

2016-10-21

The Discontinuous Galerkin (DG) electronic structure method employs an adaptive local basis (ALB) set to solve the Kohn-Sham equations of density functional theory in a discontinuous Galerkin framework. The adaptive local basis is generated on-the-fly to capture the local material physics and can systematically attain chemical accuracy with only a few tens of degrees of freedom per atom. A central issue for large-scale calculations, however, is the computation of the electron density (and subsequently, ground state properties) from the discretized Hamiltonian in an efficient and scalable manner. We show in this work how Chebyshev polynomial filtered subspace iteration (CheFSI) canmore » be used to address this issue and push the envelope in large-scale materials simulations in a discontinuous Galerkin framework. We describe how the subspace filtering steps can be performed in an efficient and scalable manner using a two-dimensional parallelization scheme, thanks to the orthogonality of the DG basis set and block-sparse structure of the DG Hamiltonian matrix. The on-the-fly nature of the ALB functions requires additional care in carrying out the subspace iterations. We demonstrate the parallel scalability of the DG-CheFSI approach in calculations of large-scale twodimensional graphene sheets and bulk three-dimensional lithium-ion electrolyte systems. In conclusion, employing 55 296 computational cores, the time per self-consistent field iteration for a sample of the bulk 3D electrolyte containing 8586 atoms is 90 s, and the time for a graphene sheet containing 11 520 atoms is 75 s.« less

Astroparticle physics and cosmology.

PubMed

Mitton, Simon

2006-05-20

Astroparticle physics is an interdisciplinary field that explores the connections between the physics of elementary particles and the large-scale properties of the universe. Particle physicists have developed a standard model to describe the properties of matter in the quantum world. This model explains the bewildering array of particles in terms of constructs made from two or three quarks. Quarks, leptons, and three of the fundamental forces of physics are the main components of this standard model. Cosmologists have also developed a standard model to describe the bulk properties of the universe. In this new framework, ordinary matter, such as stars and galaxies, makes up only around 4% of the material universe. The bulk of the universe is dark matter (roughly 23%) and dark energy (about 73%). This dark energy drives an acceleration that means that the expanding universe will grow ever larger. String theory, in which the universe has several invisible dimensions, might offer an opportunity to unite the quantum description of the particle world with the gravitational properties of the large-scale universe.

Real-time atomistic observation of structural phase transformations in individual hafnia nanorods

DOE PAGES

Hudak, Bethany M.; Depner, Sean W.; Waetzig, Gregory R.; ...

2017-05-12

High-temperature phases of hafnium dioxide have exceptionally high dielectric constants and large bandgaps, but quenching them to room temperature remains a challenge. Scaling the bulk form to nanocrystals, while successful in stabilizing the tetragonal phase of isomorphous ZrO 2, has produced nanorods with a twinned version of the room temperature monoclinic phase in HfO 2. Here we use in situ heating in a scanning transmission electron microscope to observe the transformation of an HfO 2 nanorod from monoclinic to tetragonal, with a transformation temperature suppressed by over 1000°C from bulk. When the nanorod is annealed, we observe with atomic-scale resolutionmore » the transformation from twinned-monoclinic to tetragonal, starting at a twin boundary and propagating via coherent transformation dislocation; the nanorod is reduced to hafnium on cooling. Unlike the bulk displacive transition, nanoscale size-confinement enables us to manipulate the transformation mechanism, and we observe discrete nucleation events and sigmoidal nucleation and growth kinetics.« less

Impact of small-scale saline tracer heterogeneity on electrical resistivity monitoring in fully and partially saturated porous media: Insights from geoelectrical milli-fluidic experiments

NASA Astrophysics Data System (ADS)

Jougnot, Damien; Jiménez-Martínez, Joaquín; Legendre, Raphaël; Le Borgne, Tanguy; Méheust, Yves; Linde, Niklas

2018-03-01

Time-lapse electrical resistivity tomography (ERT) is a geophysical method widely used to remotely monitor the migration of electrically-conductive tracers and contaminant plumes in the subsurface. Interpretations of time-lapse ERT inversion results are generally based on the assumption of a homogeneous solute concentration below the resolution limits of the tomogram depicting inferred electrical conductivity variations. We suggest that ignoring small-scale solute concentration variability (i.e., at the sub-resolution scale) is a major reason for the often-observed apparent loss of solute mass in ERT tracer studies. To demonstrate this, we developed a geoelectrical milli-fluidic setup where the bulk electric conductivity of a 2D analogous porous medium, consisting of cylindrical grains positioned randomly inside a Hele-Shaw cell, is monitored continuously in time while saline tracer tests are performed through the medium under fully and partially saturated conditions. High resolution images of the porous medium are recorded with a camera at regular time intervals, and provide both the spatial distribution of the fluid phases (aqueous solution and air), and the saline solute concentration field (where the solute consists of a mixture of salt and fluorescein, the latter being used as a proxy for the salt concentration). Effective bulk electrical conductivities computed numerically from the measured solute concentration field and the spatial distributions of fluid phases agree well with the measured bulk conductivities. We find that the effective bulk electrical conductivity is highly influenced by the connectivity of high electrical conductivity regions. The spatial distribution of air, saline tracer fingering, and mixing phenomena drive temporal changes in the effective bulk electrical conductivity by creating preferential paths or barriers for electrical current at the pore-scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical conductivity, especially for partially saturated conditions. We highlight how these phenomena contribute to the typically large apparent mass loss observed when conducting field-scale time-lapse ERT.

Large temporal scale and capacity subsurface bulk energy storage with CO2

NASA Astrophysics Data System (ADS)

Saar, M. O.; Fleming, M. R.; Adams, B. M.; Ogland-Hand, J.; Nelson, E. S.; Randolph, J.; Sioshansi, R.; Kuehn, T. H.; Buscheck, T. A.; Bielicki, J. M.

2017-12-01

Decarbonizing energy systems by increasing the penetration of variable renewable energy (VRE) technologies requires efficient and short- to long-term energy storage. Very large amounts of energy can be stored in the subsurface as heat and/or pressure energy in order to provide both short- and long-term (seasonal) storage, depending on the implementation. This energy storage approach can be quite efficient, especially where geothermal energy is naturally added to the system. Here, we present subsurface heat and/or pressure energy storage with supercritical carbon dioxide (CO2) and discuss the system's efficiency, deployment options, as well as its advantages and disadvantages, compared to several other energy storage options. CO2-based subsurface bulk energy storage has the potential to be particularly efficient and large-scale, both temporally (i.e., seasonal) and spatially. The latter refers to the amount of energy that can be stored underground, using CO2, at a geologically conducive location, potentially enabling storing excess power from a substantial portion of the power grid. The implication is that it would be possible to employ centralized energy storage for (a substantial part of) the power grid, where the geology enables CO2-based bulk subsurface energy storage, whereas the VRE technologies (solar, wind) are located on that same power grid, where (solar, wind) conditions are ideal. However, this may require reinforcing the power grid's transmission lines in certain parts of the grid to enable high-load power transmission from/to a few locations.

Mesoscopic Free Path of Nonthermalized Photogenerated Carriers in a Ferroelectric Insulator.

PubMed

Gu, Zongquan; Imbrenda, Dominic; Bennett-Jackson, Andrew L; Falmbigl, Matthias; Podpirka, Adrian; Parker, Thomas C; Shreiber, Daniel; Ivill, Mathew P; Fridkin, Vladimir M; Spanier, Jonathan E

2017-03-03

We show how finite-size scaling of a bulk photovoltaic effect-generated electric field in epitaxial ferroelectric insulating BaTiO_{3}(001) films and a photo-Hall response involving the bulk photovoltaic current reveal a large room-temperature mean free path of photogenerated nonthermalized electrons. Experimental determination of mesoscopic ballistic optically generated carrier transport opens a new paradigm for hot electron-based solar energy conversion, and for facile control of ballistic transport distinct from existing low-dimensional semiconductor interfaces, surfaces, layers, or other structures.

Large-scale structure in brane-induced gravity. I. Perturbation theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scoccimarro, Roman

2009-11-15

We study the growth of subhorizon perturbations in brane-induced gravity using perturbation theory. We solve for the linear evolution of perturbations taking advantage of the symmetry under gauge transformations along the extra-dimension to decouple the bulk equations in the quasistatic approximation, which we argue may be a better approximation at large scales than thought before. We then study the nonlinearities in the bulk and brane equations, concentrating on the workings of the Vainshtein mechanism by which the theory becomes general relativity (GR) at small scales. We show that at the level of the power spectrum, to a good approximation, themore » effect of nonlinearities in the modified gravity sector may be absorbed into a renormalization of the gravitational constant. Since the relation between the lensing potential and density perturbations is entirely unaffected by the extra physics in these theories, the modified gravity can be described in this approximation by a single function, an effective gravitational constant for nonrelativistic motion that depends on space and time. We develop a resummation scheme to calculate it, and provide predictions for the nonlinear power spectrum. At the level of the large-scale bispectrum, the leading order corrections are obtained by standard perturbation theory techniques, and show that the suppression of the brane-bending mode leads to characteristic signatures in the non-Gaussianity generated by gravity, generic to models that become GR at small scales through second-derivative interactions. We compare the predictions in this work to numerical simulations in a companion paper.« less

Large scale structure in universes dominated by cold dark matter

NASA Technical Reports Server (NTRS)

Bond, J. Richard

1986-01-01

The theory of Gaussian random density field peaks is applied to a numerical study of the large-scale structure developing from adiabatic fluctuations in models of biased galaxy formation in universes with Omega = 1, h = 0.5 dominated by cold dark matter (CDM). The angular anisotropy of the cross-correlation function demonstrates that the far-field regions of cluster-scale peaks are asymmetric, as recent observations indicate. These regions will generate pancakes or filaments upon collapse. One-dimensional singularities in the large-scale bulk flow should arise in these CDM models, appearing as pancakes in position space. They are too rare to explain the CfA bubble walls, but pancakes that are just turning around now are sufficiently abundant and would appear to be thin walls normal to the line of sight in redshift space. Large scale streaming velocities are significantly smaller than recent observations indicate. To explain the reported 700 km/s coherent motions, mass must be significantly more clustered than galaxies with a biasing factor of less than 0.4 and a nonlinear redshift at cluster scales greater than one for both massive neutrino and cold models.

First measurement of the bulk flow of nearby galaxies using the cosmic microwave background

NASA Astrophysics Data System (ADS)

Lavaux, Guilhem; Afshordi, Niayesh; Hudson, Michael J.

2013-04-01

Peculiar velocities in the nearby Universe can be measured via the kinetic Sunyaev-Zel'dovich (kSZ) effect. Using a statistical method based on an optimized cross-correlation with nearby galaxies, we extract the kSZ signal generated by plasma halo of galaxies from the cosmic microwave background (CMB) temperature anisotropies observed by the Wilkinson Microwave Anisotropy Probe (WMAP). Marginalizing over the thermal Sunyaev-Zel'dovich contribution from clusters of galaxies, possible unresolved point source contamination, and Galactic foregrounds, we find a kSZ bulk flow signal present at the ˜90 per cent confidence level in the seven-year WMAP data. When only galaxies within 50 h-1 Mpc are included in the kSZ template, we find a bulk flow in the CMB frame of |V| = 533 ± 263 km s-1, in the direction l = 324 ± 27, b = -7 ± 17, consistent with bulk flow measurements on a similar scale using classical distance indicators. We show how this comparison constrains, for the first time, the (ionized) baryonic budget in the local universe. On very large (˜500 h-1 Mpc) scales, we find a 95 per cent upper limit of 470 km s-1, inconsistent with some analyses of bulk flow of clusters from the kSZ. We estimate that the significance of the bulk flow signal may increase to 3σ-5σ using data from the Planck probe.

Why small-scale cannabis growers stay small: five mechanisms that prevent small-scale growers from going large scale.

PubMed

Hammersvik, Eirik; Sandberg, Sveinung; Pedersen, Willy

2012-11-01

Over the past 15-20 years, domestic cultivation of cannabis has been established in a number of European countries. New techniques have made such cultivation easier; however, the bulk of growers remain small-scale. In this study, we explore the factors that prevent small-scale growers from increasing their production. The study is based on 1 year of ethnographic fieldwork and qualitative interviews conducted with 45 Norwegian cannabis growers, 10 of whom were growing on a large-scale and 35 on a small-scale. The study identifies five mechanisms that prevent small-scale indoor growers from going large-scale. First, large-scale operations involve a number of people, large sums of money, a high work-load and a high risk of detection, and thus demand a higher level of organizational skills than for small growing operations. Second, financial assets are needed to start a large 'grow-site'. Housing rent, electricity, equipment and nutrients are expensive. Third, to be able to sell large quantities of cannabis, growers need access to an illegal distribution network and knowledge of how to act according to black market norms and structures. Fourth, large-scale operations require advanced horticultural skills to maximize yield and quality, which demands greater skills and knowledge than does small-scale cultivation. Fifth, small-scale growers are often embedded in the 'cannabis culture', which emphasizes anti-commercialism, anti-violence and ecological and community values. Hence, starting up large-scale production will imply having to renegotiate or abandon these values. Going from small- to large-scale cannabis production is a demanding task-ideologically, technically, economically and personally. The many obstacles that small-scale growers face and the lack of interest and motivation for going large-scale suggest that the risk of a 'slippery slope' from small-scale to large-scale growing is limited. Possible political implications of the findings are discussed. Copyright © 2012 Elsevier B.V. All rights reserved.

Anisotropic modulus stabilisation: strings at LHC scales with micron-sized extra dimensions

NASA Astrophysics Data System (ADS)

Cicoli, M.; Burgess, C. P.; Quevedo, F.

2011-10-01

We construct flux-stabilised Type IIB string compactifications whose extra dimensions have very different sizes, and use these to describe several types of vacua with a TeV string scale. Because we can access regimes where two dimensions are hierarchically larger than the other four, we find examples where two dimensions are micron-sized while the other four are at the weak scale in addition to more standard examples with all six extra dimensions equally large. Besides providing ultraviolet completeness, the phenomenology of these models is richer than vanilla large-dimensional models in several generic ways: ( i) they are supersymmetric, with supersymmetry broken at sub-eV scales in the bulk but only nonlinearly realised in the Standard Model sector, leading to no MSSM superpartners for ordinary particles and many more bulk missing-energy channels, as in supersymmetric large extra dimensions (SLED); ( ii) small cycles in the more complicated extra-dimensional geometry allow some KK states to reside at TeV scales even if all six extra dimensions are nominally much larger; ( iii) a rich spectrum of string and KK states at TeV scales; and ( iv) an equally rich spectrum of very light moduli exist having unusually small (but technically natural) masses, with potentially interesting implications for cosmology and astrophysics that nonetheless evade new-force constraints. The hierarchy problem is solved in these models because the extra-dimensional volume is naturally stabilised at exponentially large values: the extra dimensions are Calabi-Yau geometries with a 4D K3 or T 4-fibration over a 2D base, with moduli stabilised within the well-established LARGE-Volume scenario. The new technical step is the use of poly-instanton corrections to the superpotential (which, unlike for simpler models, are likely to be present on K3 or T 4-fibered Calabi-Yau compactifications) to obtain a large hierarchy between the sizes of different dimensions. For several scenarios we identify the low-energy spectrum and briefly discuss some of their astrophysical, cosmological and phenomenological implications.

Enhanced peculiar velocities in brane-induced gravity

NASA Astrophysics Data System (ADS)

Wyman, Mark; Khoury, Justin

2010-08-01

The mounting evidence for anomalously large peculiar velocities in our Universe presents a challenge for the ΛCDM paradigm. The recent estimates of the large-scale bulk flow by Watkins et al. are inconsistent at the nearly 3σ level with ΛCDM predictions. Meanwhile, Lee and Komatsu have recently estimated that the occurrence of high-velocity merging systems such as the bullet cluster (1E0657-57) is unlikely at a 6.5-5.8σ level, with an estimated probability between 3.3×10-11 and 3.6×10-9 in ΛCDM cosmology. We show that these anomalies are alleviated in a broad class of infrared-modifed gravity theories, called brane-induced gravity, in which gravity becomes higher-dimensional at ultralarge distances. These theories include additional scalar forces that enhance gravitational attraction and therefore speed up structure formation at late times and on sufficiently large scales. The peculiar velocities are enhanced by 24-34% compared to standard gravity, with the maximal enhancement nearly consistent at the 2σ level with bulk flow observations. The occurrence of the bullet cluster in these theories is ≈104 times more probable than in ΛCDM cosmology.

Enhanced peculiar velocities in brane-induced gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wyman, Mark; Khoury, Justin

The mounting evidence for anomalously large peculiar velocities in our Universe presents a challenge for the {Lambda}CDM paradigm. The recent estimates of the large-scale bulk flow by Watkins et al. are inconsistent at the nearly 3{sigma} level with {Lambda}CDM predictions. Meanwhile, Lee and Komatsu have recently estimated that the occurrence of high-velocity merging systems such as the bullet cluster (1E0657-57) is unlikely at a 6.5-5.8{sigma} level, with an estimated probability between 3.3x10{sup -11} and 3.6x10{sup -9} in {Lambda}CDM cosmology. We show that these anomalies are alleviated in a broad class of infrared-modifed gravity theories, called brane-induced gravity, in which gravitymore » becomes higher-dimensional at ultralarge distances. These theories include additional scalar forces that enhance gravitational attraction and therefore speed up structure formation at late times and on sufficiently large scales. The peculiar velocities are enhanced by 24-34% compared to standard gravity, with the maximal enhancement nearly consistent at the 2{sigma} level with bulk flow observations. The occurrence of the bullet cluster in these theories is {approx_equal}10{sup 4} times more probable than in {Lambda}CDM cosmology.« less

Competitive adsorption in model charged protein mixtures: Equilibrium isotherms and kinetics behavior

NASA Astrophysics Data System (ADS)

Fang, F.; Szleifer, I.

2003-07-01

The competitive adsorption of proteins of different sizes and charges is studied using a molecular theory. The theory enables the study of charged systems explicitly including the size, shape, and charge distributions in all the molecular species in the mixture. Thus, this approach goes beyond the commonly used Poisson-Boltzmann approximation. The adsorption isotherms of the protein mixtures are studied for mixtures of two proteins of different size and charge. The amount of proteins adsorbed and the fraction of each protein is calculated as a function of the bulk composition of the solution and the amount of salt in the system. It is found that the total amount of proteins adsorbed is a monotonically decreasing function of the fraction of large proteins on the bulk solution and for fixed protein composition of the salt concentration. However, the composition of the adsorbed layer is a complicated function of the bulk composition and solution ionic strength. The structure of the adsorb layer depends upon the bulk composition and salt concentration. In general, there are multilayers adsorbed due to the long-range character of the electrostatic interactions. When the composition of large proteins in bulk is in very large excess it is found that the structure of the adsorb multilayer is such that the layer in contact with the surface is composed by a mixture of large and small proteins. However, the second and third layers are almost exclusively composed of large proteins. The theory is also generalized to study the time-dependent adsorption. The approach is based on separation of time scales into fast modes for the ions from the salt and the solvent and slow for the proteins. The dynamic equations are written for the slow modes, while the fast ones are obtained from the condition of equilibrium constrained to the distribution of proteins given by the slow modes. Two different processes are presented: the adsorption from a homogeneous solution to a charged surface at low salt concentration, and large excess of the large proteins in bulk. The second process is the kinetics of structural and adsorption change by changing the salt concentration of the bulk solution from low to high. The first process shows a large overshoot of the large proteins on the surface due to their excess in solution, followed by a surface replacement by the smaller molecules. The second process shows a very fast desorption of the large proteins followed by adsorption at latter stages. This process is found to be driven by large electrostatic repulsions induced by the fast ions from the salt approaching the surface. The relevance of the theoretical predictions to experimental system and possible directions for improvements of the theory are discussed.

Analysis of Surface and Bulk Behavior in Ni-Pd Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Noebe, Rondald D.

2003-01-01

The most salient features of the surface structure and bulk behavior of Ni-Pd alloys have been studied using the BFS method for alloys. Large-scale atomistic simulations were performed to investigate surface segregation profiles as a function of temperature, crystal face, and composition. Pd enrichment of the first layer was observed in (111) and (100) surfaces, and enrichment of the top two layers occurred for (110) surfaces. In all cases, the segregation profile shows alternate planes enriched and depleted in Pd. In addition, the phase structure of bulk Ni-Pd alloys as a function of temperature and composition was studied. A weak ordering tendency was observed at low temperatures, which helps explain the compositional oscillations in the segregation profiles. Finally, based on atom-by-atom static energy calculations, a comprehensive explanation for the observed surface and bulk features will be presented in terms of competing chemical and strain energy effects.

Impact of Utility-Scale Distributed Wind on Transmission-Level System Operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brancucci Martinez-Anido, C.; Hodge, B. M.

2014-09-01

This report presents a new renewable integration study that aims to assess the potential for adding distributed wind to the current power system with minimal or no upgrades to the distribution or transmission electricity systems. It investigates the impacts of integrating large amounts of utility-scale distributed wind power on bulk system operations by performing a case study on the power system of the Independent System Operator-New England (ISO-NE).

A cosmic superfluid phase

NASA Technical Reports Server (NTRS)

Gradwohl, Ben-Ami

1991-01-01

The universe may have undergone a superfluid-like phase during its evolution, resulting from the injection of nontopological charge into the spontaneously broken vacuum. In the presence of vortices this charge is identified with angular momentum. This leads to turbulent domains on the scale of the correlation length. By restoring the symmetry at low temperatures, the vortices dissociate and push the charges to the boundaries of these domains. The model can be scaled (phenomenologically) to very low energies, it can be incorporated in a late time phase transition and form large scale structure in the boundary layers of the correlation volumes. The novel feature of the model lies in the fact that the dark matter is endowed with coherent motion. The possibilities of identifying this flow around superfluid vortices with the observed large scale bulk motion is discussed. If this identification is possible, then the definite prediction can be made that a more extended map of peculiar velocities would have to reveal large scale circulations in the flow pattern.

Large-scale structure from cosmic-string loops in a baryon-dominated universe

NASA Technical Reports Server (NTRS)

Melott, Adrian L.; Scherrer, Robert J.

1988-01-01

The results are presented of a numerical simulation of the formation of large-scale structure in a universe with Omega(0) = 0.2 and h = 0.5 dominated by baryons in which cosmic strings provide the initial density perturbations. The numerical model yields a power spectrum. Nonlinear evolution confirms that the model can account for 700 km/s bulk flows and a strong cluster-cluster correlation, but does rather poorly on smaller scales. There is no visual 'filamentary' structure, and the two-point correlation has too steep a logarithmic slope. The value of G mu = 4 x 10 to the -6th is significantly lower than previous estimates for the value of G mu in baryon-dominated cosmic string models.

Ultra-large distance modification of gravity from Lorentz symmetry breaking at the Planck scale

NASA Astrophysics Data System (ADS)

Gorbunov, Dmitry S.; Sibiryakov, Sergei M.

2005-09-01

We present an extension of the Randall-Sundrum model in which, due to spontaneous Lorentz symmetry breaking, graviton mixes with bulk vector fields and becomes quasilocalized. The masses of KK modes comprising the four-dimensional graviton are naturally exponentially small. This allows to push the Lorentz breaking scale to as high as a few tenth of the Planck mass. The model does not contain ghosts or tachyons and does not exhibit the van Dam-Veltman-Zakharov discontinuity. The gravitational attraction between static point masses becomes gradually weaker with increasing of separation and gets replaced by repulsion (antigravity) at exponentially large distances.

Two-Level Chebyshev Filter Based Complementary Subspace Method: Pushing the Envelope of Large-Scale Electronic Structure Calculations.

PubMed

Banerjee, Amartya S; Lin, Lin; Suryanarayana, Phanish; Yang, Chao; Pask, John E

2018-06-12

We describe a novel iterative strategy for Kohn-Sham density functional theory calculations aimed at large systems (>1,000 electrons), applicable to metals and insulators alike. In lieu of explicit diagonalization of the Kohn-Sham Hamiltonian on every self-consistent field (SCF) iteration, we employ a two-level Chebyshev polynomial filter based complementary subspace strategy to (1) compute a set of vectors that span the occupied subspace of the Hamiltonian; (2) reduce subspace diagonalization to just partially occupied states; and (3) obtain those states in an efficient, scalable manner via an inner Chebyshev filter iteration. By reducing the necessary computation to just partially occupied states and obtaining these through an inner Chebyshev iteration, our approach reduces the cost of large metallic calculations significantly, while eliminating subspace diagonalization for insulating systems altogether. We describe the implementation of the method within the framework of the discontinuous Galerkin (DG) electronic structure method and show that this results in a computational scheme that can effectively tackle bulk and nano systems containing tens of thousands of electrons, with chemical accuracy, within a few minutes or less of wall clock time per SCF iteration on large-scale computing platforms. We anticipate that our method will be instrumental in pushing the envelope of large-scale ab initio molecular dynamics. As a demonstration of this, we simulate a bulk silicon system containing 8,000 atoms at finite temperature, and obtain an average SCF step wall time of 51 s on 34,560 processors; thus allowing us to carry out 1.0 ps of ab initio molecular dynamics in approximately 28 h (of wall time).

Cast aluminium single crystals cross the threshold from bulk to size-dependent stochastic plasticity

NASA Astrophysics Data System (ADS)

Krebs, J.; Rao, S. I.; Verheyden, S.; Miko, C.; Goodall, R.; Curtin, W. A.; Mortensen, A.

2017-07-01

Metals are known to exhibit mechanical behaviour at the nanoscale different to bulk samples. This transition typically initiates at the micrometre scale, yet existing techniques to produce micrometre-sized samples often introduce artefacts that can influence deformation mechanisms. Here, we demonstrate the casting of micrometre-scale aluminium single-crystal wires by infiltration of a salt mould. Samples have millimetre lengths, smooth surfaces, a range of crystallographic orientations, and a diameter D as small as 6 μm. The wires deform in bursts, at a stress that increases with decreasing D. Bursts greater than 200 nm account for roughly 50% of wire deformation and have exponentially distributed intensities. Dislocation dynamics simulations show that single-arm sources that produce large displacement bursts halted by stochastic cross-slip and lock formation explain microcast wire behaviour. This microcasting technique may be extended to several other metals or alloys and offers the possibility of exploring mechanical behaviour spanning the micrometre scale.

Radar detection of Phobos

NASA Technical Reports Server (NTRS)

Ostro, S. J.; Jurgens, R. F.; Yeomans, D. K.; Standish, E. M.; Greiner, W.

1989-01-01

Radar echoes from the martian satellite Phobos provide information about that object's surface properties at scales near the 3.5-cm observing wavelength. Phobos appears less rough than the moon at centimeter-to-decimeter scales. The uppermost few decimeters of the satellite's regolith have a mean bulk density within 20 percent of 2.0 g/cu cm. The radar signature of Phobos (albedo, polarization ratio, and echo spectral shape) differs from signatures measured for small, earth-approaching objects, but resembles those of large (greater than 100-km), C-class, mainbelt asteroids.

An extended algebraic variational multiscale-multigrid-multifractal method (XAVM4) for large-eddy simulation of turbulent two-phase flow

NASA Astrophysics Data System (ADS)

Rasthofer, U.; Wall, W. A.; Gravemeier, V.

2018-04-01

A novel and comprehensive computational method, referred to as the eXtended Algebraic Variational Multiscale-Multigrid-Multifractal Method (XAVM4), is proposed for large-eddy simulation of the particularly challenging problem of turbulent two-phase flow. The XAVM4 involves multifractal subgrid-scale modeling as well as a Nitsche-type extended finite element method as an approach for two-phase flow. The application of an advanced structural subgrid-scale modeling approach in conjunction with a sharp representation of the discontinuities at the interface between two bulk fluids promise high-fidelity large-eddy simulation of turbulent two-phase flow. The high potential of the XAVM4 is demonstrated for large-eddy simulation of turbulent two-phase bubbly channel flow, that is, turbulent channel flow carrying a single large bubble of the size of the channel half-width in this particular application.

Accurate modeling of defects in graphene transport calculations

NASA Astrophysics Data System (ADS)

Linhart, Lukas; Burgdörfer, Joachim; Libisch, Florian

2018-01-01

We present an approach for embedding defect structures modeled by density functional theory into large-scale tight-binding simulations. We extract local tight-binding parameters for the vicinity of the defect site using Wannier functions. In the transition region between the bulk lattice and the defect the tight-binding parameters are continuously adjusted to approach the bulk limit far away from the defect. This embedding approach allows for an accurate high-level treatment of the defect orbitals using as many as ten nearest neighbors while keeping a small number of nearest neighbors in the bulk to render the overall computational cost reasonable. As an example of our approach, we consider an extended graphene lattice decorated with Stone-Wales defects, flower defects, double vacancies, or silicon substitutes. We predict distinct scattering patterns mirroring the defect symmetries and magnitude that should be experimentally accessible.

Fire Whirls

NASA Astrophysics Data System (ADS)

Tohidi, Ali; Gollner, Michael J.; Xiao, Huahua

2018-01-01

Fire whirls present a powerful intensification of combustion, long studied in the fire research community because of the dangers they present during large urban and wildland fires. However, their destructive power has hidden many features of their formation, growth, and propagation. Therefore, most of what is known about fire whirls comes from scale modeling experiments in the laboratory. Both the methods of formation, which are dominated by wind and geometry, and the inner structure of the whirl, including velocity and temperature fields, have been studied at this scale. Quasi-steady fire whirls directly over a fuel source form the bulk of current experimental knowledge, although many other cases exist in nature. The structure of fire whirls has yet to be reliably measured at large scales; however, scaling laws have been relatively successful in modeling the conditions for formation from small to large scales. This review surveys the state of knowledge concerning the fluid dynamics of fire whirls, including the conditions for their formation, their structure, and the mechanisms that control their unique state. We highlight recent discoveries and survey potential avenues for future research, including using the properties of fire whirls for efficient remediation and energy generation.

Bulk silicon as photonic dynamic infrared scene projector

NASA Astrophysics Data System (ADS)

Malyutenko, V. K.; Bogatyrenko, V. V.; Malyutenko, O. Yu.

2013-04-01

A Si-based fast (frame rate >1 kHz), large-scale (scene area 100 cm2), broadband (3-12 μm), dynamic contactless infrared (IR) scene projector is demonstrated. An IR movie appears on a scene because of the conversion of a visible scenario projected at a scene kept at elevated temperature. Light down conversion comes as a result of free carrier generation in a bulk Si scene followed by modulation of its thermal emission output in the spectral band of free carrier absorption. The experimental setup, an IR movie, figures of merit, and the process's advantages in comparison to other projector technologies are discussed.

A Comprehensive Two-moment Warm Microphysical Bulk Scheme :

NASA Astrophysics Data System (ADS)

Caro, D.; Wobrock, W.; Flossmann, A.; Chaumerliac, N.

The microphysic properties of gaz, aerosol particles, and hydrometeors have impli- cations at local scale (precipitations, pollution peak,..), at regional scale (inundation, acid rains,...), and also, at global scale (radiative forcing,...). So, a multi-scale study is necessary to understand and forecast in a good way meteorological phenomena con- cerning clouds. However, it cannot be carried with detailed microphysic model, on account of computers limitations. So, microphysical bulk schemes have to estimate the n´ large scale z properties of clouds due to smaller scale processes and charac- teristics. So, the development of such bulk scheme is rather important to go further in the knowledge of earth climate and in the forecasting of intense meteorological phenomena. Here, a quasi-spectral microphysic warm scheme has been developed to predict the concentrations and mixing ratios of aerosols, cloud droplets and raindrops. It considers, explicitely and analytically, the nucleation of droplets (Abdul-Razzak et al., 2000), condensation/evaporation (Chaumerliac et al., 1987), the breakup and collision-coalescence processes with the Long (1974) Ss kernels and the Berry and ´ Reinhardt (1974) Ss autoconversion parameterization, but also, the aerosols and gaz ´ scavenging. First, the parameterization has been estimated in the simplest dynamic framework of an air parcel model, with the results of the detailed scavenging model, DESCAM (Flossmann et al., 1985). Then, it has been tested, in the dynamic frame- work of a kinematic model (Szumowski et al., 1998) dedicated to the HaRP cam- paign (Hawaiian Rainband Project, 1990), with the observations and with the results of the two dimensional detailed microphysic scheme, DESCAM 2-D (Flossmann et al., 1988), implement in the CLARK model (Clark and Farley, 1984).

Sorption Phase of Supercritical CO2 in Silica Aerogel: Experiments and Mesoscale Computer Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rother, Gernot; Vlcek, Lukas; Gruszkiewicz, Miroslaw

2014-01-01

Adsorption of supercritical CO2 in nanoporous silica aerogel was investigated by a combination of experiments and molecular-level computer modeling. High-pressure gravimetric and vibrating tube densimetry techniques were used to measure the mean pore fluid density and excess sorption at 35 C and 50 C and pressures of 0-200 bar. Densification of the pore fluid was observed at bulk fluid densities below 0.7 g/cm3. Far above the bulk fluid density, near-zero sorption or weak depletion effects were measured, while broad excess sorption maxima form in the vicinity of the bulk critical density region. The CO2 sorption properties are very similar formore » two aerogels with different bulk densities of 0.1 g/cm3 and 0.2 g/cm3, respectively. The spatial distribution of the confined supercritical fluid was analyzed in terms of sorption- and bulk-phase densities by means of the Adsorbed Phase Model (APM), which used data from gravimetric sorption and small-angle neutron scattering experiments. To gain more detailed insight into supercritical fluid sorption, large-scale lattice gas GCMC simulations were utilized and tuned to resemble the experimental excess sorption data. The computed three-dimensional pore fluid density distributions show that the observed maximum of the excess sorption near the critical density originates from large density fluctuations pinned to the pore walls. At this maximum, the size of these fluctuations is comparable to the prevailing pore sizes.« less

Time-dependent compressibility of poly (methyl methacrylate) (PMMA) : an experimental and molecular dynamics investigation

NASA Astrophysics Data System (ADS)

Sane, Sandeep Bhalchandra

This thesis contains three chapters, which describe different aspects of an investigation of the bulk response of Poly(Methyl Methacrylate) (PMMA). The first chapter describes the physical measurements by means of a Belcher/McKinney-type apparatus. Used earlier for the measurement of the bulk response of Poly(Vinyl Acetate), it was now adapted for making measurements at higher temperatures commensurate with the glass transition temperature of PMMA. The dynamic bulk compliance of PMMA was measured at atmospheric pressure over a wide range of temperatures and frequencies, from which the master curves for the bulk compliance were generated by means of the time-temperature superposition principle. It was found that the extent of the transition ranges for the bulk and shear response were comparable. Comparison of the shift factors for bulk and shear responses supports the idea that different molecular mechanisms contribute to shear and bulk deformations. The second chapter delineates molecular dynamics computations for the bulk response for a range of pressures and temperatures. The model(s) consisted of 2256 atoms formed into three polymer chains with fifty monomer units per chain per unit cell. The time scales accessed were limited to tens of pico seconds. It was found that, in addition to the typical energy minimization and temperature annealing cycles for establishing equilibrium models, it is advantageous to subject the model samples to a cycle of relatively large pressures (GPa-range) for improving the equilibrium state. On comparing the computations with the experimentally determined "glassy" behavior, one finds that, although the computations were limited to small samples in a physical sense, the primary limitation rests in the very short times (pico seconds). The molecular dynamics computations do not model the physically observed temperature sensitivity of PMMA, even if one employs a hypothetical time-temperature shift to account for the large difference in time scales between experiment and computation. The values computed by the molecular dynamics method do agree with the values measured at the coldest temperature and at the highest frequency of one kiloHertz. The third chapter draws on measurements of uniaxial, shear and Poisson response conducted previously in our laboratory. With the availability of four time or frequency-dependent material functions for the same material, the process of interconversion between different material functions was investigated. Computed material functions were evaluated against the direct experimental measurements and the limitations imposed on successful interconversion due to the experimental errors in the underlying physical data were explored. Differences were observed that are larger than the experimental errors would suggest.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaveri, Rahul A.; Shilling, John E.; Zelenyuk, Alla

Low bulk diffusivity inside viscous semisolid atmospheric secondary organic aerosol (SOA) can prolong equilibration time scale, but its broader impacts on aerosol growth and size distribution dynamics are poorly understood. In this article, we present quantitative insights into the effects of bulk diffusivity on the growth and evaporation kinetics of SOA formed under dry conditions from photooxidation of isoprene in the presence of a bimodal aerosol consisting of Aitken (ammonium sulfate) and accumulation (isoprene or α-pinene SOA) mode particles. Aerosol composition measurements and evaporation kinetics indicate that isoprene SOA is composed of several semivolatile organic compounds (SVOCs), with some reversiblymore » reacting to form oligomers. Model analysis shows that liquid-like bulk diffusivities can be used to fit the observed evaporation kinetics of accumulation mode particles but fail to explain the growth kinetics of bimodal aerosol by significantly under-predicting the evolution of the Aitken mode. In contrast, the semisolid scenario successfully reproduces both evaporation and growth kinetics, with the interpretation that hindered partitioning of SVOCs into large viscous particles effectively promotes the growth of smaller particles that have shorter diffusion time scales. This effect has important implications for the growth of atmospheric ultrafine particles to climatically active sizes.« less

Growth Kinetics and Size Distribution Dynamics of Viscous Secondary Organic Aerosol

DOE PAGES

Zaveri, Rahul A.; Shilling, John E.; Zelenyuk, Alla; ...

2017-12-15

Low bulk diffusivity inside viscous semisolid atmospheric secondary organic aerosol (SOA) can prolong equilibration time scale, but its broader impacts on aerosol growth and size distribution dynamics are poorly understood. In this article, we present quantitative insights into the effects of bulk diffusivity on the growth and evaporation kinetics of SOA formed under dry conditions from photooxidation of isoprene in the presence of a bimodal aerosol consisting of Aitken (ammonium sulfate) and accumulation (isoprene or α-pinene SOA) mode particles. Aerosol composition measurements and evaporation kinetics indicate that isoprene SOA is composed of several semivolatile organic compounds (SVOCs), with some reversiblymore » reacting to form oligomers. Model analysis shows that liquid-like bulk diffusivities can be used to fit the observed evaporation kinetics of accumulation mode particles but fail to explain the growth kinetics of bimodal aerosol by significantly under-predicting the evolution of the Aitken mode. In contrast, the semisolid scenario successfully reproduces both evaporation and growth kinetics, with the interpretation that hindered partitioning of SVOCs into large viscous particles effectively promotes the growth of smaller particles that have shorter diffusion time scales. This effect has important implications for the growth of atmospheric ultrafine particles to climatically active sizes.« less

Growth Kinetics and Size Distribution Dynamics of Viscous Secondary Organic Aerosol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaveri, Rahul A.; Shilling, John E.; Zelenyuk, Alla

Low bulk diffusivity inside viscous semisolid atmospheric secondary organic aerosol (SOA) can prolong equilibration time scale, but its broader impacts on aerosol growth and size distribution dynamics are poorly understood. In this article, we present quantitative insights into the effects of bulk diffusivity on the growth and evaporation kinetics of SOA formed under dry conditions from photooxidation of isoprene in the presence of a bimodal aerosol consisting of Aitken (ammonium sulfate) and accumulation (isoprene or α-pinene SOA) mode particles. Aerosol composition measurements and evaporation kinetics indicate that isoprene SOA is composed of several semivolatile organic compounds (SVOCs), with some reversiblymore » reacting to form oligomers. Model analysis shows that liquid-like bulk diffusivities can be used to fit the observed evaporation kinetics of accumulation mode particles but fail to explain the growth kinetics of bimodal aerosol by significantly under-predicting the evolution of the Aitken mode. In contrast, the semisolid scenario successfully reproduces both evaporation and growth kinetics, with the interpretation that hindered partitioning of SVOCs into large viscous particles effectively promotes the growth of smaller particles that have shorter diffusion time scales. This effect has important implications for the growth of atmospheric ultrafine particles to climatically active sizes.« less

Exploring the Utilization of Low-Pressure, Piston-Cylinder Experiments to Determine the Bulk Compositions of Finite, Precious Materials

NASA Technical Reports Server (NTRS)

Vander Kaaden, K. E.; McCubbin, F. M.; Harrington, A. D.

2017-01-01

Determining the bulk composition of precious materials with a finite mass (e.g., meteorite samples) is extremely important in the fields of Earth and Planetary Science. From meteorite studies we are able to place constraints on large scale planetary processes like global differentiation and subsequent volcanism, as well as smaller scale processes like crystallization in a magma chamber or sedimentary compaction at the surface. However, with meteorite samples in particular, far too often we are limited by how precious the sample is as well as its limited mass. In this study, we have utilized aliquots of samples previously studied for toxicological hazards, including both the fresh samples (lunar mare basalt NWA 4734, lunar regolith breccia NWA 7611, martian basalt Tissint, martian regolith breccia NWA 7034, a vestian basalt Berthoud, a vestian regolith breccia NWA 2060, and a terrestrial mid-ocean ridge basalt (MORB)), and those that underwent iron leaching (Tissint, NWA 7034, NWA 4734, MORB). With these small masses of material, we performed low pressure (approx. 0.75 GPa), high temperature (greater than 1600 degrees Celsius) melting experiments. Each sample was analyzed using a JEOL 8530F electron microprobe to determine the bulk composition of the materials that were previously examined. When available, the results of our microprobe data were compared with bulk rock compositions in the literature. The results of this study show that with this technique, only approx. 50 mg of sample is required to accurately determine the bulk composition of the materials of interest.

Entanglement renormalization, quantum error correction, and bulk causality

NASA Astrophysics Data System (ADS)

Kim, Isaac H.; Kastoryano, Michael J.

2017-04-01

Entanglement renormalization can be viewed as an encoding circuit for a family of approximate quantum error correcting codes. The logical information becomes progres-sively more well-protected against erasure errors at larger length scales. In particular, an approximate variant of holographic quantum error correcting code emerges at low energy for critical systems. This implies that two operators that are largely separated in scales behave as if they are spatially separated operators, in the sense that they obey a Lieb-Robinson type locality bound under a time evolution generated by a local Hamiltonian.

The Kardar-Parisi-Zhang Equation as Scaling Limit of Weakly Asymmetric Interacting Brownian Motions

NASA Astrophysics Data System (ADS)

Diehl, Joscha; Gubinelli, Massimiliano; Perkowski, Nicolas

2017-09-01

We consider a system of infinitely many interacting Brownian motions that models the height of a one-dimensional interface between two bulk phases. We prove that the large scale fluctuations of the system are well approximated by the solution to the KPZ equation provided the microscopic interaction is weakly asymmetric. The proof is based on the martingale solutions of Gonçalves and Jara (Arch Ration Mech Anal 212(2):597-644, 2014) and the corresponding uniqueness result of Gubinelli and Perkowski (Energy solutions of KPZ are unique, 2015).

Holographic curvature perturbations in a cosmology with a space-like singularity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferreira, Elisa G.M.; Brandenberger, Robert; Institute for Theoretical Studies, ETH Zürich,Clausiusstr. 47, Zürich, CH-8092

2016-07-19

We study the evolution of cosmological perturbations in an anti-de-Sitter (AdS) bulk through a cosmological singularity by mapping the dynamics onto the boundary conformal fields theory by means of the AdS/CFT correspondence. We consider a deformed AdS space-time obtained by considering a time-dependent dilaton which induces a curvature singularity in the bulk at a time which we call t=0, and which asymptotically approaches AdS both for large positive and negative times. The boundary field theory becomes free when the bulk curvature goes to infinity. Hence, the evolution of the fluctuations is under better controle on the boundary than in themore » bulk. To avoid unbounded particle production across the bounce it is necessary to smooth out the curvature singularity at very high curvatures. We show how the bulk cosmological perturbations can be mapped onto boundary gauge field fluctuations. We evolve the latter and compare the spectrum of fluctuations on the infrared scales relevant for cosmological observations before and after the bounce point. We find that the index of the power spectrum of fluctuations is the same before and after the bounce.« less

Bulk Bismuth as a High-Capacity and Ultralong Cycle-Life Anode for Sodium-Ion Batteries by Coupling with Glyme-Based Electrolytes.

PubMed

Wang, Chenchen; Wang, Liubin; Li, Fujun; Cheng, Fangyi; Chen, Jun

2017-09-01

Sodium-ion batteries (SIBs) have attracted great interest for large-scale electric energy storage in recent years. However, anodes with long cycle life and large reversible capacities are still lacking and therefore limiting the development of SIBs. Here, a bulk Bi anode with surprisingly high Na storage performance in combination with glyme-based electrolytes is reported. This study shows that the bulk Bi electrode is gradually developed into a porous integrity during initial cycling, which is totally different from that in carbonate-based electrolytes and ensures facile Na + transport and structural stability. The achievable capacity of bulk Bi in the NaPF 6 -diglyme electrolyte is high up to 400 mAh g -1 , and the capacity retention is 94.4% after 2000 cycles, corresponding to a capacity loss of 0.0028% per cycle. It exhibits two flat discharge/charge plateaus at 0.67/0.77 and 0.46/0.64 V, ascribed to the typical two-phase reactions of Bi ↔ NaBi and NaBi ↔ Na 3 Bi, respectively. The excellent performance is attributed to the unique porous integrity, stable solid electrolyte interface, and good electrode wettability of glymes. This interplay between electrolyte and electrode to boost Na storage performance will pave a new pathway for high-performance SIBs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Driving force for hydrophobic interaction at different length scales.

PubMed

Zangi, Ronen

2011-03-17

We study by molecular dynamics simulations the driving force for the hydrophobic interaction between graphene sheets of different sizes down to the atomic scale. Similar to the prediction by Lum, Chandler, and Weeks for hard-sphere solvation [J. Phys. Chem. B 1999, 103, 4570-4577], we find the driving force to be length-scale dependent, despite the fact that our model systems do not exhibit dewetting. For small hydrophobic solutes, the association is purely entropic, while enthalpy favors dissociation. The latter is demonstrated to arise from the enhancement of hydrogen bonding between the water molecules around small hydrophobes. On the other hand, the attraction between large graphene sheets is dominated by enthalpy which mainly originates from direct solute-solute interactions. The crossover length is found to be inside the range of 0.3-1.5 nm(2) of the surface area of the hydrophobe that is eliminated in the association process. In the large-scale regime, different thermodynamic properties are scalable with this change of surface area. In particular, upon dimerization, a total and a water-induced stabilization of approximately 65 and 12 kJ/mol/nm(2) are obtained, respectively, and on average around one hydrogen bond is gained per 1 nm(2) of graphene sheet association. Furthermore, the potential of mean force between the sheets is also scalable except for interplate distances smaller than 0.64 nm which corresponds to the region around the barrier for removing the last layer of water. It turns out that, as the surface area increases, the relative height of the barrier for association decreases and the range of attraction increases. It is also shown that, around small hydrophobic solutes, the lifetime of the hydrogen bonds is longer than in the bulk, while around large hydrophobes it is the same. Nevertheless, the rearrangement of the hydrogen-bond network for both length-scale regimes is slower than in bulk water. © 2011 American Chemical Society

Temperature dependence of the structural relaxation time in equilibrium below the nominal T(g): results from freestanding polymer films.

PubMed

Ngai, K L; Capaccioli, Simone; Paluch, Marian; Prevosto, Daniele

2014-05-22

When the thickness is reduced to nanometer scale, freestanding high molecular weight polymer thin films undergo large reduction of degree of cooperativity and coupling parameter n in the Coupling Model (CM). The finite-size effect together with the surfaces with high mobility make the α-relaxation time of the polymer in nanoconfinement, τ(α)(nano)(T), much shorter than τ(α)(bulk)(T) in the bulk. The consequence is avoidance of vitrification at and below the bulk glass transition temperature, T(g)(bulk), on cooling, and the freestanding polymer thin film remains at thermodynamic equilibrium at temperatures below T(g)(bulk). Molecular dynamics simulations have shown that the specific volume of the freestanding film is the same as the bulk glass-former at equilibrium at the same temperatures. Extreme nanoconfinement renders total or almost total removal of cooperativity of the α-relaxation, and τ(α)(nano)(T) becomes the same or almost the same as the JG β-relaxation time τ(β)(bulk)(T) of the bulk glass-former at equilibrium and at temperatures below T(g)(bulk). Taking advantage of being able to obtain τ(β)(bulk)(T) at equilibrium density below T(g)(bulk) by extreme nanoconfinement of the freestanding films, and using the CM relation between τ(α)(bulk)(T) and τ(β)(bulk)(T), we conclude that the Vogel-Fulcher-Tammann-Hesse (VFTH) dependence of τ(α)(bulk)(T) cannot hold for glass-formers in equilibrium at temperatures significantly below T(g)(bulk). In addition, τ(α)(bulk)(T) does not diverge at the Vogel temperature, T₀, as suggested by the VFTH-dependence and predicted by some theories of glass transition. Instead, τ(α)(bulk)(T) of the glass-former at equilibrium has a much weaker temperature dependence than the VFTH-dependence at temperature below T(g)(bulk) and even below T₀. This conclusion from our analysis is consistent with the temperature dependence of τ(α)(bulk)(T) found experimentally in polymers aged long enough time to attain the equilibrium state at various temperatures below T(g)(bulk).

Full-scale evaluation of a multi-component additive for efficient control of activated sludge filamentous bulking.

PubMed

Seka, M A; Van DeWiele, T; Verstraete, W

2002-01-01

A multi-component additive formulated for a more efficient control of activated sludge filamentous bulking was evaluated at a full-scale treatment plant experiencing severe filamentous bulking. It was found that, besides offering an immediate improvement of sludge settling, the multi-component additive was able to eliminate the filamentous bacteria causing the bulking. Hence, contrary to ordinary additives, this novel additive yielded immediate as well as long-term improvements in sludge sedimentation upon a few additions. Preliminary lab-scale toxicity tests showed that the treatment of the sludge by the additive should not impart any toxicity to the resulting effluent.

A multiscale SPH particle model of the near-wall dynamics of leukocytes in flow.

PubMed

Gholami, Babak; Comerford, Andrew; Ellero, Marco

2014-01-01

A novel multiscale Lagrangian particle solver based on SPH is developed with the intended application of leukocyte transport in large arteries. In such arteries, the transport of leukocytes and red blood cells can be divided into two distinct regions: the bulk flow and the near-wall region. In the bulk flow, the transport can be modeled on a continuum basis as the transport of passive scalar concentrations. Whereas in the near-wall region, specific particle tracking of the leukocytes is required and lubrication forces need to be separately taken into account. Because of large separation of spatio-temporal scales involved in the problem, simulations of red blood cells and leukocytes are handled separately. In order to take the exchange of leukocytes between the bulk fluid and the near-wall region into account, solutions are communicated through coupling of conserved quantities at the interface between these regions. Because the particle tracking is limited to those leukocytes lying in the near-wall region only, our approach brings considerable speedup to the simulation of leukocyte circulation in a test geometry of a backward-facing step, which encompasses many flow features observed in vivo. Copyright © 2013 John Wiley & Sons, Ltd.

Spatial variability of shelf sediments in the STRATAFORM natural laboratory, Northern California

USGS Publications Warehouse

Goff, J.A.; Wheatcroft, R.A.; Lee, H.; Drake, D.E.; Swift, D.J.P.; Fan, S.

2002-01-01

The "Correlation Length Experiment", an intensive box coring effort on the Eel River shelf (Northern California) in the summer of 1997, endeavored to characterize the lateral variability of near-surface shelf sediments over scales of meters to kilometers. Coring focused on two sites, K60 and S60, separated by ??? 15 km along the 60 m isobath. The sites are near the sand-to-mud transition, although K60 is sandier owing to its proximity to the Eel River mouth. Nearly 140 cores were collected on dip and strike lines with core intervals from < 10m to 1 km. Measurements on each core included bulk density computed from gamma-ray attenuation, porosity converted from resistivity measurements, and surficial grain size. Grain size was also measured over the full depth range within a select subset of cores. X-radiograph images were also examined. Semi-variograms were computed for strike, dip, and down-hole directions at each site. The sand-to-mud transition exerts a strong influence on all measurements: on average, bulk density increases and porosity decreases with regional increases in mean grain size. Analysis of bulk density measurements indicates very strong contrasts in the sediment variability at K60 and S60. No coherent bedding is seen at K60; in the strike direction, horizontal variability is "white" (fully uncorrelated) from the smallest scales examined (a few meters) to the largest (8 km), with a variance equal to that seen within the cores. In contrast, coherent bedding exists at S60 related to the preservation of the 1995 flood deposit. A correlatable structure is found in the strike direction with a decorrelation distance of ??? 800 m, and can be related to long-wavelength undulations in the topography and/or thickness of the flood layer or overburden. We hypothesize that the high degree of bulk density variability at K60 is a result of more intense physical reworking of the seabed in the sandier environment. Without significant averaging, the resistivity-based porosity measurements are only marginally correlated to gamma-ray-bulk density measurements, and are largely independent of mean grain size. Furthermore, porosity displays a high degree of incoherent variability at both sites. Porosity, with a much smaller sample volume than bulk density, may therefore resolve small-scale biogenic variability which is filtered out in the bulk density measurement. ?? 2002 Elsevier Science Ltd. All rights reserved.

Impurity engineering of Czochralski silicon used for ultra large-scaled-integrated circuits

NASA Astrophysics Data System (ADS)

Yang, Deren; Chen, Jiahe; Ma, Xiangyang; Que, Duanlin

2009-01-01

Impurities in Czochralski silicon (Cz-Si) used for ultra large-scaled-integrated (ULSI) circuits have been believed to deteriorate the performance of devices. In this paper, a review of the recent processes from our investigation on internal gettering in Cz-Si wafers which were doped with nitrogen, germanium and/or high content of carbon is presented. It has been suggested that those impurities enhance oxygen precipitation, and create both denser bulk microdefects and enough denuded zone with the desirable width, which is benefit of the internal gettering of metal contamination. Based on the experimental facts, a potential mechanism of impurity doping on the internal gettering structure is interpreted and, a new concept of 'impurity engineering' for Cz-Si used for ULSI is proposed.

Production of large-scale, freestanding vanadium pentoxide nanobelt porous structures

NASA Astrophysics Data System (ADS)

Yun, Yong Ju; Kim, Byung Hoon; Hong, Won G.; Kim, Chang Hee; Kim, Yark Yeon; Jeong, Eun-Ju; Jang, Won Ick; Yu, Han Young

2012-02-01

Large-scale, freestanding, porous structures of vanadium pentoxide nanobelts (VPNs) were successfully prepared using the template-free freeze-drying method. The porous and multi-layered VPN macrostructures are composed of randomly oriented long nanobelts (over 100 μm) and their side length can be controlled up to a few tens of centimetres. Also, the bulk density and surface area of these macrostructures are 3-5 mg cm-3 and 40-80 m2 g-1, respectively, which are similar to those of the excellent adsorbents. In addition, the removal efficiency measurements of ammonia molecules revealed that the VPN porous structures can adsorb the ammonia molecules with the combinations of van der Waals forces and strong chemical bonding by functional groups on the VPN surface.

Production of large-scale, freestanding vanadium pentoxide nanobelt porous structures.

PubMed

Yun, Yong Ju; Kim, Byung Hoon; Hong, Won G; Kim, Chang Hee; Kim, Yark Yeon; Jeong, Eun-ju; Jang, Won Ick; Yu, Han Young

2012-03-07

Large-scale, freestanding, porous structures of vanadium pentoxide nanobelts (VPNs) were successfully prepared using the template-free freeze-drying method. The porous and multi-layered VPN macrostructures are composed of randomly oriented long nanobelts (over 100 μm) and their side length can be controlled up to a few tens of centimetres. Also, the bulk density and surface area of these macrostructures are 3-5 mg cm(-3) and 40-80 m(2) g(-1), respectively, which are similar to those of the excellent adsorbents. In addition, the removal efficiency measurements of ammonia molecules revealed that the VPN porous structures can adsorb the ammonia molecules with the combinations of van der Waals forces and strong chemical bonding by functional groups on the VPN surface.

Scaling Trends and Tradeoffs between Short Channel Effect and Channel Boosting Characteristics in Sub-20 nm Bulk/Silicon-on-Insulator NAND Flash Memory

NASA Astrophysics Data System (ADS)

Miyaji, Kousuke; Hung, Chinglin; Takeuchi, Ken

2012-04-01

The scaling trends and limitation in sub-20 nm a bulk and silicon-on-insulator (SOI) NAND flash memory is studied by the three-dimensional (3D) device simulation focusing on short channel effects (SCE), channel boost leakage and channel voltage boosting characteristics during the program-inhibit operation. Although increasing punch-through stopper doping concentration is effective for suppressing SCE in bulk NAND cells, the generation of junction leakage becomes serious. On the other hand, SCE can be suppressed by thinning the buried oxide (BOX) in SOI NAND cells. However, the boosted channel voltage decreases by the higher BOX capacitance. It is concluded that the scaling limitation is dominated by the junction leakage and channel boosting capability for bulk and SOI NAND flash cells, respectively, and the scaling limit is decreased to 9 nm using SOI NAND flash memory cells from 13 nm in bulk NAND flash memory cells.

Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of their Matter Content

NASA Technical Reports Server (NTRS)

Georganopoulos, Markos; Kazanas, Demosthenes; Perlman, Eric; Stecker, Floyd W.

2004-01-01

We propose a method for estimating the composition, i.e. the relative amounts of leptons and protons, of extragalactic jets which exhibit Chandra - detected knots in their kpc scale jets. The method relies on measuring, or setting upper limits on, the component of the Cosmic Microwave Background (CMB) radiation that is bulk-Comptonized by the cold electrons in the relativistically flowing jet. These measurements, along with modeling of the broadband knot emission that constrain the bulk Lorentz factor GAMMA of the jets, can yield estimates of the jet power carried by protons and leptons. We provide an explicit calculation of the spectrum of the bulk-Comptonized (BC) CMB component and apply these results to PKS 0637 - 752 and 3C 273, two superluminal quasars with Chandra - detected large scale jets. What makes these sources particularly suited for such a procedure is the absence of significant non-thermal jet emission in the 'bridge', the region between the core and the first bright jet knot, which guarantees that most of the electrons are cold there, leaving the BC scattered CMB radiation as the only significant source of photons in this region. At lambda = 3.6 - 8.0 microns, the most likely band to observe the BC scattered CMB emission, the Spitzer angular resolution (approximately 1" - 3") is considerably smaller than the the 'bridges' of these jets (approximately 10"), making it possible to both measure and resolve this emission.

Simultaneous Study of Intake and In-Cylinder IC Engine Flow Fields to Provide an Insight into Intake Induced Cyclic Variations

NASA Astrophysics Data System (ADS)

Justham, T.; Jarvis, S.; Clarke, A.; Garner, C. P.; Hargrave, G. K.; Halliwell, N. A.

2006-07-01

Simultaneous intake and in-cylinder digital particle image velocimetry (DPIV) experimental data is presented for a motored spark ignition (SI) optical internal combustion (IC) engine. Two individual DPIV systems were employed to study the inter-relationship between the intake and in-cylinder flow fields at an engine speed of 1500 rpm. Results for the intake runner velocity field at the time of maximum intake valve lift are compared to incylinder velocity fields later in the same engine cycle. Relationships between flow structures within the runner and cylinder were seen to be strong during the intake stroke but less significant during compression. Cyclic variations within the intake runner were seen to affect the large scale bulk flow motion. The subsequent decay of the large scale motions into smaller scale turbulent structures during the compression stroke appear to reduce the relationship with the intake flow variations.

Large-Scale Biomonitoring of Remote and Threatened Ecosystems via High-Throughput Sequencing

PubMed Central

Gibson, Joel F.; Shokralla, Shadi; Curry, Colin; Baird, Donald J.; Monk, Wendy A.; King, Ian; Hajibabaei, Mehrdad

2015-01-01

Biodiversity metrics are critical for assessment and monitoring of ecosystems threatened by anthropogenic stressors. Existing sorting and identification methods are too expensive and labour-intensive to be scaled up to meet management needs. Alternately, a high-throughput DNA sequencing approach could be used to determine biodiversity metrics from bulk environmental samples collected as part of a large-scale biomonitoring program. Here we show that both morphological and DNA sequence-based analyses are suitable for recovery of individual taxonomic richness, estimation of proportional abundance, and calculation of biodiversity metrics using a set of 24 benthic samples collected in the Peace-Athabasca Delta region of Canada. The high-throughput sequencing approach was able to recover all metrics with a higher degree of taxonomic resolution than morphological analysis. The reduced cost and increased capacity of DNA sequence-based approaches will finally allow environmental monitoring programs to operate at the geographical and temporal scale required by industrial and regulatory end-users. PMID:26488407

Contact resistance change memory using N-doped Cr2Ge2Te6 phase-change material showing non-bulk resistance change

NASA Astrophysics Data System (ADS)

Shuang, Y.; Sutou, Y.; Hatayama, S.; Shindo, S.; Song, Y. H.; Ando, D.; Koike, J.

2018-04-01

Phase-change random access memory (PCRAM) is enabled by a large resistance contrast between amorphous and crystalline phases upon reversible switching between the two states. Thus, great efforts have been devoted to identifying potential phase-change materials (PCMs) with large electrical contrast to realize a more accurate reading operation. In contrast, although the truly dominant resistance in a scaled PCRAM cell is contact resistance, less attention has been paid toward the investigation of the contact property between PCMs and electrode metals. This study aims to propose a non-bulk-resistance-dominant PCRAM whose resistance is modulated only by contact. The contact-resistance-dominated PCM exploited here is N-doped Cr2Ge2Te6 (NCrGT), which exhibits almost no electrical resistivity difference between the two phases but exhibits a typical switching behavior involving a three-order-of-magnitude SET/RESET resistance ratio owing to its large contact resistance contrast. The conduction mechanism was discussed on the basis of current-voltage characteristics of the interface between the NCrGT and the W electrode.

Elastocapillarity: When Surface Tension Deforms Elastic Solids

NASA Astrophysics Data System (ADS)

Bico, José; Reyssat, Étienne; Roman, Benoît

2018-01-01

Although negligible at large scales, capillary forces may become dominant for submillimetric objects. Surface tension is usually associated with the spherical shape of small droplets and bubbles, wetting phenomena, imbibition, or the motion of insects at the surface of water. However, beyond liquid interfaces, capillary forces can also deform solid bodies in their bulk, as observed in recent experiments with very soft gels. Capillary interactions, which are responsible for the cohesion of sandcastles, can also bend slender structures and induce the bundling of arrays of fibers. Thin sheets can spontaneously wrap liquid droplets within the limit of the constraints dictated by differential geometry. This review aims to describe the different scaling parameters and characteristic lengths involved in elastocapillarity. We focus on three main configurations, each characterized by a specific dimension: three-dimensional (3D), deformations induced in bulk solids; 1D, bending and bundling of rod-like structures; and 2D, bending and stretching of thin sheets. Although each configuration deserves a detailed review, we hope our broad description provides a general view of elastocapillarity.

Size scales over which ordinary chondrites and their parent asteroids are homogeneous in oxidation state and oxygen-isotopic composition

NASA Astrophysics Data System (ADS)

Rubin, Alan E.; Ziegler, Karen; Young, Edward D.

2008-02-01

Literature data demonstrate that on a global, asteroid-wide scale (plausibly on the order of 100 km), ordinary chondrites (OC) have heterogeneous oxidation states and O-isotopic compositions (represented, respectively, by the mean olivine Fa and bulk Δ 17O compositions of equilibrated samples). Samples analyzed here include: (a) two H5 chondrite Antarctic finds (ALHA79046 and TIL 82415) that have the same cosmic-ray exposure age (7.6 Ma) and were probably within ˜1 km of each other when they were excavated from the H-chondrite parent body, (b) different individual stones from the Holbrook L/LL6 fall that were probably within ˜1 m of each other when their parent meteoroid penetrated the Earth's atmosphere, and (c) drill cores from a large slab of the Estacado H6 find located within a few tens of centimeters of each other. Our results indicate that OC are heterogeneous in their bulk oxidation state and O-isotopic composition on 100-km-size scales, but homogeneous on meter-, decimeter- and centimeter-size scales. (On kilometer size scales, oxidation state is heterogeneous, but O isotopes appear to be homogeneous.) The asteroid-wide heterogeneity in oxidation state and O-isotopic composition was inherited from the solar nebula. The homogeneity on small size scales was probably caused in part by fluid-assisted metamorphism and mainly by impact-gardening processes (which are most effective at mixing target materials on scales of ⩽1 m).

GSD-1G and MPI-DING Reference Glasses for In Situ and Bulk Isotopic Determination

USGS Publications Warehouse

Jochum, K.P.; Wilson, S.A.; Abouchami, W.; Amini, M.; Chmeleff, J.; Eisenhauer, A.; Hegner, E.; Iaccheri, L.M.; Kieffer, B.; Krause, J.; McDonough, W.F.; Mertz-Kraus, R.; Raczek, I.; Rudnick, R.L.; Scholz, Donna K.; Steinhoefel, G.; Stoll, B.; Stracke, A.; Tonarini, S.; Weis, D.; Weis, U.; Woodhead, J.D.

2011-01-01

This paper contains the results of an extensive isotopic study of United States Geological Survey GSD-1G and MPI-DING reference glasses. Thirteen different laboratories were involved using high-precision bulk (TIMS, MC-ICP-MS) and microanalytical (LA-MC-ICP-MS, LA-ICP-MS) techniques. Detailed studies were performed to demonstrate the large-scale and small-scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD-1G and the MPI-DING glasses are suitable reference materials for microanalytical and bulk analytical purposes. Ce document contient les r??sultats d'une importante ??tude isotopique des verres de r??f??rence USGS GSD-1G et MPI-DING. Treize laboratoires diff??rents ont particip?? au travers de techniques analytiques de haute pr??cision travaillant soit sur ??chantillon total (TIMS, MC-ICP-MS) soit par microanalyse ??in situ?? (LA-MC-ICP-MS, LA-ICP-MS). ?? 2010 The Authors. Geostandards and Geoanalytical Research ?? 2010 International Association of Geoanalysts.

Paleomagnetism of a primitive achondrite parent body: The acapulcoite-lodranites

NASA Astrophysics Data System (ADS)

Schnepf, N. R.; Weiss, B. P.; Andrade Lima, E.; Fu, R. R.; Uehara, M.; Gattacceca, J.; Wang, H.; Suavet, C. R.

2014-12-01

Primitive achondrites are a recently recognized meteorite grouping with textures and compositions intermediate between unmelted meteorites (chondrites) and igneous meteorites (achondrites). Their existence demonstrates prima facie that some planetesimals only experienced partial rather than complete melting. We present the first paleomagnetic measurements of acapulcoite-lodranite meteorites to determine the existence and intensity of ancient magnetic fields on their parent body. Our paleomagnetic study tests the hypothesis that their parent body had an advecting metallic core, with the goal of providing one of the first geophysical constraints on its large-scale structure and the extent of interior differentiation. In particular, by analyzing samples whose petrologic textures require an origin on a partially differentiated body, we will be able to critically test a recent proposal that some achondrites and chondrite groups could have originated on a single body (Weiss and Elkins-Tanton 2013). We analyzed samples of the meteorites Acapulco and Lodran. Like other acapulcoites and lodranites, these meteorites are granular rocks containing large (~0.1-0.3 mm) kamacite and taenite grains along with similarly sized silicate crystals. Many silicate grains contain numerous fine (1-10 μm) FeNi metal inclusions. Our compositional measurements and rock magnetic data suggest that tetrataenite is rare or absent. Bulk paleomagnetic measurements were done on four mutually oriented bulk samples of Acapulco and one bulk sample of Lodran. Alternating field (AF) demagnetization revealed that the magnetization of the bulk samples is highly unstable, likely due to the large (~0.1-0.3 mm) interstitial kamacite grains throughout the samples. To overcome this challenge, we are analyzing individual ~0.2 mm mutually oriented silicate grains extracted using a wire saw micromill. Preliminary SQUID microscopy measurements of a Lodran silicate grain suggest magnetization stable to AF levels of at least 25-40 mT.

ALMA Observations of a Quiescent Molecular Cloud in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Wong, Tony; Hughes, Annie; Tokuda, Kazuki; Indebetouw, Rémy; Bernard, Jean-Philippe; Onishi, Toshikazu; Wojciechowski, Evan; Bandurski, Jeffrey B.; Kawamura, Akiko; Roman-Duval, Julia; Cao, Yixian; Chen, C.-H. Rosie; Chu, You-hua; Cui, Chaoyue; Fukui, Yasuo; Montier, Ludovic; Muller, Erik; Ott, Juergen; Paradis, Deborah; Pineda, Jorge L.; Rosolowsky, Erik; Sewiło, Marta

2017-12-01

We present high-resolution (subparsec) observations of a giant molecular cloud in the nearest star-forming galaxy, the Large Magellanic Cloud. ALMA Band 6 observations trace the bulk of the molecular gas in 12CO(2-1) and the high column density regions in 13CO(2-1). Our target is a quiescent cloud (PGCC G282.98-32.40, which we refer to as the “Planck cold cloud” or PCC) in the southern outskirts of the galaxy where star formation activity is very low and largely confined to one location. We decompose the cloud into structures using a dendrogram and apply an identical analysis to matched-resolution cubes of the 30 Doradus molecular cloud (located near intense star formation) for comparison. Structures in the PCC exhibit roughly 10 times lower surface density and five times lower velocity dispersion than comparably sized structures in 30 Dor, underscoring the non-universality of molecular cloud properties. In both clouds, structures with relatively higher surface density lie closer to simple virial equilibrium, whereas lower surface-density structures tend to exhibit supervirial line widths. In the PCC, relatively high line widths are found in the vicinity of an infrared source whose properties are consistent with a luminous young stellar object. More generally, we find that the smallest resolved structures (“leaves”) of the dendrogram span close to the full range of line widths observed across all scales. As a result, while the bulk of the kinetic energy is found on the largest scales, the small-scale energetics tend to be dominated by only a few structures, leading to substantial scatter in observed size-line-width relationships.

The Characterization of Grade PCEA Recycle Graphite Pilot Scale Billets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burchell, Timothy D; Pappano, Peter J

2010-10-01

Here we report the physical properties of a series specimens machined from pilot scale (~ 152 mm diameter x ~305 mm length) grade PCEA recycle billets manufactured by GrafTech. The pilot scale billets were processed with increasing amounts of (unirradiated) graphite (from 20% to 100%) introduced to the formulation with the goal of determining if large fractions of recycle graphite have a deleterious effect on properties. The properties determined include Bulk Density, Electrical Resistivity, Elastic (Young s) Modulus, and Coefficient of Thermal Expansion. Although property variations were observed to be correlated with the recycle fraction, the magnitude of the variationsmore » was noted to be small.« less

Hybridization of active and passive elements for planar photonic components and interconnects

NASA Astrophysics Data System (ADS)

Pearson, M.; Bidnyk, S.; Balakrishnan, A.

2007-02-01

The deployment of Passive Optical Networks (PON) for Fiber-to-the-Home (FTTH) applications currently represents the fastest growing sector of the telecommunication industry. Traditionally, FTTH transceivers have been manufactured using commodity bulk optics subcomponents, such as thin film filters (TFFs), micro-optic collimating lenses, TO-packaged lasers, and photodetectors. Assembling these subcomponents into a single housing requires active alignment and labor-intensive techniques. Today, the majority of cost reducing strategies using bulk subcomponents has been implemented making future reductions in the price of manufacturing FTTH transceivers unlikely. Future success of large scale deployments of FTTH depends on further cost reductions of transceivers. Realizing the necessity of a radically new packaging approach for assembly of photonic components and interconnects, we designed a novel way of hybridizing active and passive elements into a planar lightwave circuit (PLC) platform. In our approach, all the filtering components were monolithically integrated into the chip using advancements in planar reflective gratings. Subsequently, active components were passively hybridized with the chip using fully-automated high-capacity flip-chip bonders. In this approach, the assembly of the transceiver package required no active alignment and was readily suitable for large-scale production. This paper describes the monolithic integration of filters and hybridization of active components in both silica-on-silicon and silicon-on-insulator PLCs.

Exploring the Potential Business Case for Synergies Between Natural Gas and Renewable Energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cochran, Jaquelin; Zinaman, Owen; Logan, Jeffrey

2014-02-01

Natural gas and renewable energy each contribute to economic growth, energy independence, and carbon mitigation, sometimes independently and sometimes collectively. Often, natural gas and renewables are considered competitors in markets, such as those for bulk electricity. This paper attempts to address the question, 'Given near- and long-term needs for abundant, cleaner energy sources and decarbonization, how can more compelling business models be created so that these two domestic forms of energy work in greater concert?' This paper explores revenue opportunities that emerge from systems-level perspectives in 'bulk energy' (large-scale electricity and natural gas production, transmission, and trade) and four 'distributionmore » edge' subsectors: industrial, residential, commercial, and transportation end uses.« less

Comparison of the effects of platinum and CeO2 on the properties of single grain, Sm-Ba-Cu-O bulk superconductors

NASA Astrophysics Data System (ADS)

Zhao, Wen; Shi, Yunhua; Radušovská, Monika; Dennis, Anthony R.; Durrell, John H.; Diko, Pavel; Cardwell, David A.

2016-12-01

SmBa2Cu3O7-δ (Sm-123) is a light-rare-earth barium-cuprate (LRE-BCO) high-temperature superconductor (HTS) with significant potential for high field industrial applications. We report the fabrication of large, single grain bulk [Sm-Ba-Cu-O (SmBCO)] superconductors containing 1 wt% CeO2 and 0.1 wt% Pt using a top-seeded melt growth process. The performance of the SmBCO bulk superconductors containing the different dopants was evaluated based on an analysis of their superconducting properties, including critical transition temperature, T c and critical current density, J c , and on sample microstructure. We find that both CeO2 and Pt dopants refine the size of Sm2BaCuO5 (Sm-211) particles trapped in the Sm-123 superconducting phase matrix, which act as effective flux pinning centres, although the addition of CeO2 results in broadly improved superconducting performance of the fully processed bulk single grain. However, 1 wt% CeO2 is significantly cheaper than 0.1 wt% Pt, which has clear economic benefits for use in medium to large scale production processes for these technologically important materials. Finally, the use of CeO2 results generally in the formation of finer Sm-211 particles and to the generation of fewer macro-cracks and Sm-211 free regions in the sample microstructure.

Multi-scale predictive modeling of nano-material and realistic electron devices

NASA Astrophysics Data System (ADS)

Palaria, Amritanshu

Among the challenges faced in further miniaturization of electronic devices, heavy influence of the detailed atomic configuration of the material(s) involved, which often differs significantly from that of the bulk material(s), is prominent. Device design has therefore become highly interrelated with material engineering at the atomic level. This thesis aims at outlining, with examples, a multi-scale simulation procedure that allows one to integrate material and device aspects of nano-electronic design to predict behavior of novel devices with novel material. This is followed in four parts: (1) An approach that combines a higher time scale reactive force field analysis with density functional theory to predict structure of new material is demonstrated for the first time for nanowires. Novel stable structures for very small diameter silicon nanowires are predicted. (2) Density functional theory is used to show that the new nanowire structures derived in 1 above have properties different from diamond core wires even though the surface bonds in some may be similar to the surface of bulk silicon. (3) Electronic structure of relatively large-scale germanium sections of realistically strained Si/strained Ge/ strained Si nanowire heterostructures is computed using empirical tight binding and it is shown that the average non-homogeneous strain in these structures drives their interesting non-conventional electronic characteristics such as hole effective masses which decrease as the wire cross-section is reduced. (4) It is shown that tight binding, though empirical in nature, is not necessarily limited to the material and atomic structure for which the parameters have been empirically derived, but that simple changes may adapt the derived parameters to new bond environments. Si (100) surface electronic structure is obtained from bulk Si parameters.

Surface Composition of NiPd Alloys

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Khalil, Joe; Bozzolo, Guillermo; Gray, Hugh R. (Technical Monitor)

2002-01-01

Surface segregation in Ni-Pd alloys has been studied using the BFS method for alloys. Not only does the method predict an oscillatory segregation profile but it also indicates that the number of Pd-enriched surface planes can vary as a function of orientation. The segregation profiles were computed as a function of temperature, crystal face, and composition. Pd enrichment of the first layer is observed in (111) and (100) surfaces, and enrichment of the top two layers occurs for (110) surfaces. In all cases, the segregation profile shows oscillations that are actually related to weak ordering tendencies in the bulk. An atom-by-atom analysis was performed to identify the competing mechanisms leading to the observed surface behaviors. Large-scale atomistic simulations were also performed to investigate the temperature dependence of the segregation profiles as well as for analysis of the bulk structures. Finally, the observed surface behaviors are discussed in relation to the bulk phase structure of Ni-Pd alloys, which exhibit a tendency to weakly order.

Bulk antimony sulfide with excellent cycle stability as next-generation anode for lithium-ion batteries

PubMed Central

Yu, Denis Y. W.; Hoster, Harry E.; Batabyal, Sudip K.

2014-01-01

Nanomaterials as anode for lithium-ion batteries (LIB) have gained widespread interest in the research community. However, scaling up and processibility are bottlenecks to further commercialization of these materials. Here, we report that bulk antimony sulfide with a size of 10–20 μm exhibits a high capacity and stable cycling of 800 mAh g−1. Mechanical and chemical stabilities of the electrodes are ensured by an optimal electrode-electrolyte system design, with a polyimide-based binder together with fluoroethylene carbonate in the electrolyte. The polyimide binder accommodates the volume expansion during alloying process and fluoroethylene carbonate suppresses the increase in charge transfer resistance of the electrodes. We observed that particle size is not a major factor affecting the charge-discharge capacities, rate capability and stability of the material. Despite the large particle size, bulk antimony sulfide shows excellent rate performance with a capacity of 580 mAh g−1 at a rate of 2000 mA g−1. PMID:24691396

In silico screening of drug-membrane thermodynamics reveals linear relations between bulk partitioning and the potential of mean force

NASA Astrophysics Data System (ADS)

Menichetti, Roberto; Kanekal, Kiran H.; Kremer, Kurt; Bereau, Tristan

2017-09-01

The partitioning of small molecules in cell membranes—a key parameter for pharmaceutical applications—typically relies on experimentally available bulk partitioning coefficients. Computer simulations provide a structural resolution of the insertion thermodynamics via the potential of mean force but require significant sampling at the atomistic level. Here, we introduce high-throughput coarse-grained molecular dynamics simulations to screen thermodynamic properties. This application of physics-based models in a large-scale study of small molecules establishes linear relationships between partitioning coefficients and key features of the potential of mean force. This allows us to predict the structure of the insertion from bulk experimental measurements for more than 400 000 compounds. The potential of mean force hereby becomes an easily accessible quantity—already recognized for its high predictability of certain properties, e.g., passive permeation. Further, we demonstrate how coarse graining helps reduce the size of chemical space, enabling a hierarchical approach to screening small molecules.

Spectral enstrophy budget in a shear-less flow with turbulent/non-turbulent interface

NASA Astrophysics Data System (ADS)

Cimarelli, Andrea; Cocconi, Giacomo; Frohnapfel, Bettina; De Angelis, Elisabetta

2015-12-01

A numerical analysis of the interaction between decaying shear free turbulence and quiescent fluid is performed by means of global statistical budgets of enstrophy, both, at the single-point and two point levels. The single-point enstrophy budget allows us to recognize three physically relevant layers: a bulk turbulent region, an inhomogeneous turbulent layer, and an interfacial layer. Within these layers, enstrophy is produced, transferred, and finally destroyed while leading to a propagation of the turbulent front. These processes do not only depend on the position in the flow field but are also strongly scale dependent. In order to tackle this multi-dimensional behaviour of enstrophy in the space of scales and in physical space, we analyse the spectral enstrophy budget equation. The picture consists of an inviscid spatial cascade of enstrophy from large to small scales parallel to the interface moving towards the interface. At the interface, this phenomenon breaks, leaving place to an anisotropic cascade where large scale structures exhibit only a cascade process normal to the interface thus reducing their thickness while retaining their lengths parallel to the interface. The observed behaviour could be relevant for both the theoretical and the modelling approaches to flow with interacting turbulent/nonturbulent regions. The scale properties of the turbulent propagation mechanisms highlight that the inviscid turbulent transport is a large-scale phenomenon. On the contrary, the viscous diffusion, commonly associated with small scale mechanisms, highlights a much richer physics involving small lengths, normal to the interface, but at the same time large scales, parallel to the interface.

A Langevin approach to multi-scale modeling

DOE PAGES

Hirvijoki, Eero

2018-04-13

In plasmas, distribution functions often demonstrate long anisotropic tails or otherwise significant deviations from local Maxwellians. The tails, especially if they are pulled out from the bulk, pose a serious challenge for numerical simulations as resolving both the bulk and the tail on the same mesh is often challenging. A multi-scale approach, providing evolution equations for the bulk and the tail individually, could offer a resolution in the sense that both populations could be treated on separate meshes or different reduction techniques applied to the bulk and the tail population. In this paper, we propose a multi-scale method which allowsmore » us to split a distribution function into a bulk and a tail so that both populations remain genuine, non-negative distribution functions and may carry density, momentum, and energy. The proposed method is based on the observation that the motion of an individual test particle in a plasma obeys a stochastic differential equation, also referred to as a Langevin equation. Finally, this allows us to define transition probabilities between the bulk and the tail and to provide evolution equations for both populations separately.« less

A Langevin approach to multi-scale modeling

NASA Astrophysics Data System (ADS)

Hirvijoki, Eero

2018-04-01

In plasmas, distribution functions often demonstrate long anisotropic tails or otherwise significant deviations from local Maxwellians. The tails, especially if they are pulled out from the bulk, pose a serious challenge for numerical simulations as resolving both the bulk and the tail on the same mesh is often challenging. A multi-scale approach, providing evolution equations for the bulk and the tail individually, could offer a resolution in the sense that both populations could be treated on separate meshes or different reduction techniques applied to the bulk and the tail population. In this letter, we propose a multi-scale method which allows us to split a distribution function into a bulk and a tail so that both populations remain genuine, non-negative distribution functions and may carry density, momentum, and energy. The proposed method is based on the observation that the motion of an individual test particle in a plasma obeys a stochastic differential equation, also referred to as a Langevin equation. This allows us to define transition probabilities between the bulk and the tail and to provide evolution equations for both populations separately.

A Langevin approach to multi-scale modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirvijoki, Eero

In plasmas, distribution functions often demonstrate long anisotropic tails or otherwise significant deviations from local Maxwellians. The tails, especially if they are pulled out from the bulk, pose a serious challenge for numerical simulations as resolving both the bulk and the tail on the same mesh is often challenging. A multi-scale approach, providing evolution equations for the bulk and the tail individually, could offer a resolution in the sense that both populations could be treated on separate meshes or different reduction techniques applied to the bulk and the tail population. In this paper, we propose a multi-scale method which allowsmore » us to split a distribution function into a bulk and a tail so that both populations remain genuine, non-negative distribution functions and may carry density, momentum, and energy. The proposed method is based on the observation that the motion of an individual test particle in a plasma obeys a stochastic differential equation, also referred to as a Langevin equation. Finally, this allows us to define transition probabilities between the bulk and the tail and to provide evolution equations for both populations separately.« less

Large-scale Patterns of 14C Age of Bulk Organic Carbon and Various Molecular Components in Grassland Soils

NASA Astrophysics Data System (ADS)

Jia, J.; Liu, Z.; Cao, Z.; Chen, L.; He, J. S.; Haghipour, N.; Wacker, L.; Eglinton, T. I.; Feng, X.

2017-12-01

Unraveling the fate of organic carbon (OC) in soils is essential to understanding the impact of global changes on the global carbon cycle. Previous studies have shown that while various soil OC components have different decomposability, chemically labile OC can have old 14C ages. However, few studies have compared the 14C age of various soil OC components on a large scale, which may provide important information on the link between the age or turnover of soil OC components to their sources, molecular structures as well as environmental variables. In this project, a suite of soil profiles were sampled along a large-scale transect of temperate and alpine grasslands across the Tibetan and Mongolian Plateaus in China with contrasting climatic, vegetation and soil properties. Bulk OC and source-specific compounds (including fatty acids (FAs), diacids (DAs) and lignin phenols) were radiocarbon-dated to investigate the age and turnover dynamics of different OC pools and the mechanisms controlling their stability. Our results show that lignin phenols displayed a large 14C variability. Short-chain (C16, 18) FAs sourced from vascular plants as well as microorganisms were younger than plant-derived long-chain FAs and DAs, indicating that short-chain FAs were easier to be decomposed or newly synthesized. In the temperate grasslands, long-chain DAs were younger than FAs, while the opposite trend was observed in the alpine grasslands. Preliminary correlation analysis suggests that the age of short-chain FAs were mainly influenced by clay contents and climate, while reactive minerals, clay or silt particles were important factors in the stabilization of long-chain FAs, DAs and lignin phenols. Overall, our study provided a unique 14 C dataset of soil OC components in grasslands, which will provide important constraints on soil carbon turnover in future investigations.

Solar Wind Turbulent Cascade from MHD to Sub-ion Scales: Large-size 3D Hybrid Particle-in-cell Simulations

NASA Astrophysics Data System (ADS)

Franci, Luca; Landi, Simone; Verdini, Andrea; Matteini, Lorenzo; Hellinger, Petr

2018-01-01

Properties of the turbulent cascade from fluid to kinetic scales in collisionless plasmas are investigated by means of large-size 3D hybrid (fluid electrons, kinetic protons) particle-in-cell simulations. Initially isotropic Alfvénic fluctuations rapidly develop a strongly anisotropic turbulent cascade, mainly in the direction perpendicular to the ambient magnetic field. The omnidirectional magnetic field spectrum shows a double power-law behavior over almost two decades in wavenumber, with a Kolmogorov-like index at large scales, a spectral break around ion scales, and a steepening at sub-ion scales. Power laws are also observed in the spectra of the ion bulk velocity, density, and electric field, at both magnetohydrodynamic (MHD) and kinetic scales. Despite the complex structure, the omnidirectional spectra of all fields at ion and sub-ion scales are in remarkable quantitative agreement with those of a 2D simulation with similar physical parameters. This provides a partial, a posteriori validation of the 2D approximation at kinetic scales. Conversely, at MHD scales, the spectra of the density and of the velocity (and, consequently, of the electric field) exhibit differences between the 2D and 3D cases. Although they can be partly ascribed to the lower spatial resolution, the main reason is likely the larger importance of compressible effects in the full 3D geometry. Our findings are also in remarkable quantitative agreement with solar wind observations.

A critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for Late Cretaceous global correlation

NASA Astrophysics Data System (ADS)

Wendler, Ines

2013-11-01

Climate variability is driven by a complex interplay of global-scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter-regional correlation, which in most cases cannot be obtained with biostratigraphic methods alone. Chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high-resolution correlation over large distances, but complications arise from a multitude of possible influences from local differences in biological, diagenetic and physico-chemical factors on individual δ13C records that can mask the global signal. To better assess the global versus local contribution in a δ13C record it is necessary to compare numerous isotopic records on a global scale. As a contribution to this objective, this paper reviews bulk sediment δ13Ccarb records from the Late Cretaceous in order to identify differences and similarities in secular δ13C trends that help establish a global reference δ13C record for this period. The study presents a global-scale comparison of twenty δ13C records from sections representing various palaeo-latitudes in both hemispheres and different oceanic settings from the Boreal, Tethys, Western Interior, Indian Ocean and Pacific Ocean, and with various diagenetic overprinting. The isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute δ13C values and variation in amplitude between the sites. These differences reflect the varying local influences e.g. from depositional settings, bottom water age and diagenetic history, whereas the concordant patterns in δ13C shifts might represent δ13C fluctuations in the global seawater dissolved inorganic carbon. The latter is modulated by variations in organic matter burial relative to re-mineralization, in the global-scale formation of authigenic carbonate, and in partitioning of carbon between organic carbon and carbonate sinks. These variations are mainly controlled by changes in climate and eustasy. Additionally, some globally synchronous shifts in the bulk δ13Ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment. Formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and, thus, can be globally synchronized by fluctuations in eustasy, atmospheric and oceanic oxygen levels or in large-scale oceanic circulation. Because the influence of early diagenetic cements on the bulk δ13Ccarb signal can, but need not be synchronized, chemostratigraphy should not be used as a stand-alone method for trans-continental correlation, and especially minor isotopic shifts have to be interpreted with utmost care. Nevertheless, the observed consistency of the δ13C correlations confirms global scale applicability of bulk sediment δ13C chemostratigraphy for the Late Cretaceous, including sediments that underwent lithification and burial diagenesis such as the sediments from the Himalayan and Alpine sections. Limitations arise from increased uncertainties (1) in sediments with very low carbonate content, (2) from larger δ13C variability in sediments from very shallow marine environments, (3) from unrecognized hiatuses or strong changes in sedimentation rates, and (4) in sections with short stratigraphic coverage or with few biostratigraphic marker horizons.

Dynamic structural disorder in supported nanoscale catalysts

NASA Astrophysics Data System (ADS)

Rehr, J. J.; Vila, F. D.

2014-04-01

We investigate the origin and physical effects of "dynamic structural disorder" (DSD) in supported nano-scale catalysts. DSD refers to the intrinsic fluctuating, inhomogeneous structure of such nano-scale systems. In contrast to bulk materials, nano-scale systems exhibit substantial fluctuations in structure, charge, temperature, and other quantities, as well as large surface effects. The DSD is driven largely by the stochastic librational motion of the center of mass and fluxional bonding at the nanoparticle surface due to thermal coupling with the substrate. Our approach for calculating and understanding DSD is based on a combination of real-time density functional theory/molecular dynamics simulations, transient coupled-oscillator models, and statistical mechanics. This approach treats thermal and dynamic effects over multiple time-scales, and includes bond-stretching and -bending vibrations, and transient tethering to the substrate at longer ps time-scales. Potential effects on the catalytic properties of these clusters are briefly explored. Model calculations of molecule-cluster interactions and molecular dissociation reaction paths are presented in which the reactant molecules are adsorbed on the surface of dynamically sampled clusters. This model suggests that DSD can affect both the prefactors and distribution of energy barriers in reaction rates, and thus can significantly affect catalytic activity at the nano-scale.

High-resolution (SIMS) versus bulk sulfur isotope patterns of pyrite in Proterozoic microbialites with diverse mat textures

NASA Astrophysics Data System (ADS)

Gomes, M. L.; Fike, D. A.; Bergmann, K.; Knoll, A. H.

2015-12-01

Sulfur (S) isotope signatures of sedimentary pyrite preserved in marine rocks provide a rich suite of information about changes in biogeochemical cycling associated with the evolution of microbial metabolisms and oxygenation of Earth surface environments. Conventionally, these S isotope records are based on bulk rock measurements. Yet, in modern microbial mat environments, S isotope compositions of sulfide can vary by up to 40‰ over a spatial range of ~ 1 mm. Similar ranges of S isotope variability have been found in Archean pyrite grains using both Secondary Ion Mass Spectrometry and other micro-analytical techniques. These micron-scale patterns have been linked to changes in rates of microbial sulfate reduction and/or sulfide oxidation, isotopic distillation of the sulfate reservoir due to microbial sulfate reduction, and post-depositional alteration. Fine-scale mapping of S isotope compositions of pyrite can thus be used to differentiate primary environmental signals from post-depositional overprinting - improving our understanding of both. Here, we examine micron-scale S isotope patterns of pyrite in microbialites from the Mesoproterozoic-Neoproterozoic Sukhaya Tunguska Formation and Neoproterozoic Draken Formation in order to explore S isotope variability associated with different mat textures and pyrite grain morphologies. A primary goal is to link modern observations of how sulfide spatial isotope distributions reflect active microbial communities present at given depths in the mats to ancient processes driving fine-sale pyrite variability in microbialites. We find large (up to 60‰) S isotope variability within a spatial range of less than 2.5cm. The micron-scale S isotope measurements converge around the S isotope composition of pyrite extracted from bulk samples of the same microbialites. These micron-scale pyrite S isotope patterns have the potential to reveal important information about ancient biogeochemical cycling in Proterozoic mat environments with implications for interpreting S isotope signatures from the geological record.

A quenched study of the Schrödinger functional with chirally rotated boundary conditions: Applications

NASA Astrophysics Data System (ADS)

González López, J.; Jansen, K.; Renner, D. B.; Shindler, A.

2013-02-01

In a previous paper (González López, et al., 2013) [1], we have discussed the non-perturbative tuning of the chirally rotated Schrödinger functional (χSF). This tuning is required to eliminate bulk O(a) cutoff effects in physical correlation functions. Using our tuning results obtained in González López et al. (2013) [1] we perform scaling and universality tests analyzing the residual O(a) cutoff effects of several step-scaling functions and we compute renormalization factors at the matching scale. As an example of possible application of the χSF we compute the renormalized strange quark mass using large volume data obtained from Wilson twisted mass fermions at maximal twist.

Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.

PubMed

Luo, Junhang; Wang, Jiangwei; Bitzek, Erik; Huang, Jian Yu; Zheng, He; Tong, Limin; Yang, Qing; Li, Ju; Mao, Scott X

2016-01-13

Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.

Flexo-photovoltaic effect

NASA Astrophysics Data System (ADS)

Yang, Ming-Min; Kim, Dong Jik; Alexe, Marin

2018-05-01

It is highly desirable to discover photovoltaic mechanisms that enable enhanced efficiency of solar cells. Here we report that the bulk photovoltaic effect, which is free from the thermodynamic Shockley-Queisser limit but usually manifested only in noncentrosymmetric (piezoelectric or ferroelectric) materials, can be realized in any semiconductor, including silicon, by mediation of flexoelectric effect. We used either an atomic force microscope or a micrometer-scale indentation system to introduce strain gradients, thus creating very large photovoltaic currents from centrosymmetric single crystals of strontium titanate, titanium dioxide, and silicon. This strain gradient–induced bulk photovoltaic effect, which we call the flexo-photovoltaic effect, functions in the absence of a p-n junction. This finding may extend present solar cell technologies by boosting the solar energy conversion efficiency from a wide pool of established semiconductors.

Large Scale Helium Liquefaction and Considerations for Site Services for a Plant Located in Algeria

NASA Astrophysics Data System (ADS)

Froehlich, P.; Clausen, J. J.

2008-03-01

The large-scale liquefaction of helium extracted from natural gas is depicted. Based on a block diagram the process chain, starting with the pipeline downstream of the natural-gas plant to the final storage of liquid helium, is explained. Information will be provided about the recent experiences during installation and start-up of a bulk helium liquefaction plant located in Skikda, Algeria, including part-load operation based on a reduced feed gas supply. The local working and ambient conditions are described, including challenging logistic problems like shipping and receiving of parts, qualified and semi-qualified subcontractors, basic provisions and tools on site, and precautions to sea water and ambient conditions. Finally, the differences in commissioning (technically and evaluation of time and work packages) to European locations and standards will be discussed.

Digital selective growth of a ZnO nanowire array by large scale laser decomposition of zinc acetate.

PubMed

Hong, Sukjoon; Yeo, Junyeob; Manorotkul, Wanit; Kang, Hyun Wook; Lee, Jinhwan; Han, Seungyong; Rho, Yoonsoo; Suh, Young Duk; Sung, Hyung Jin; Ko, Seung Hwan

2013-05-07

We develop a digital direct writing method for ZnO NW micro-patterned growth on a large scale by selective laser decomposition of zinc acetate. For ZnO NW growth, by replacing the bulk heating with the scanning focused laser as a fully digital local heat source, zinc acetate crystallites can be selectively activated as a ZnO seed pattern to grow ZnO nanowires locally on a larger area. Together with the selective laser sintering process of metal nanoparticles, more than 10,000 UV sensors have been demonstrated on a 4 cm × 4 cm glass substrate to develop all-solution processible, all-laser mask-less digital fabrication of electronic devices including active layer and metal electrodes without any conventional vacuum deposition, photolithographic process, premade mask, high temperature and vacuum environment.

Large-eddy simulation of turbulent flow with a surface-mounted two-dimensional obstacle

NASA Technical Reports Server (NTRS)

Yang, Kyung-Soo; Ferziger, Joel H.

1993-01-01

In this paper, we perform a large eddy simulation (LES) of turbulent flow in a channel containing a two-dimensional obstacle on one wall using a dynamic subgrid-scale model (DSGSM) at Re = 3210, based on bulk velocity above the obstacle and obstacle height; the wall layers are fully resolved. The low Re enables us to perform a DNS (Case 1) against which to validate the LES results. The LES with the DSGSM is designated Case 2. In addition, an LES with the conventional fixed model constant (Case 3) is conducted to allow identification of improvements due to the DSGSM. We also include LES at Re = 82,000 (Case 4) using conventional Smagorinsky subgrid-scale model and a wall-layer model. The results will be compared with the experiment of Dimaczek et al.

Aspects of AdS/CFT: Conformal Deformations and the Goldstone Equivalence Theorem

NASA Astrophysics Data System (ADS)

Cantrell, Sean Andrew

The AdS/CFT correspondence provides a map from the states of theories situated in AdSd+1 to those in dual conformal theories in a d-dimensional space. The correspondence can be used to establish certain universal properties of some theories in one space by examining the behave of general objects in the other. In this thesis, we develop various formal aspects of AdS/CFT. Conformal deformations manifest in the AdS/CFT correspondence as boundary conditions on the AdS field. Heretofore, double-trace deformations have been the primary focus in this context. To better understand multitrace deformations, we revisit the relationship between the generating AdS partition function for a free bulk theory and the boundary CFT partition function subject to arbitrary conformal deformations. The procedure leads us to a formalism that constructs bulk fields from boundary operators. We independently replicate the holographic RG flow narrative to go on to interpret the brane used to regulate the AdS theory as a renormalization scale. The scale-dependence of the dilatation spectrum of a boundary theory in the presence of general deformations can be thus understood on the AdS side using this formalism. The Goldstone equivalence theorem allows one to relate scattering amplitudes of massive gauge fields to those of scalar fields in the limit of large scattering energies. We generalize this theorem under the framework of the AdS/CFT correspondence. First, we obtain an expression of the equivalence theorem in terms of correlation functions of creation and annihilation operators by using an AdS wave function approach to the AdS/CFT dictionary. It is shown that the divergence of the non-conserved conformal current dual to the bulk gauge field is approximately primary when computing correlators for theories in which the masses of all the exchanged particles are sufficiently large. The results are then generalized to higher spin fields. We then go on to generalize the theorem using conformal blocks in two and four-dimensional CFTs. We show that when the scaling dimensions of the exchanged operators are large compared to both their spins and the dimension of the current, the conformal blocks satisfy an equivalence theorem.

Continuous Flow Polymer Synthesis toward Reproducible Large-Scale Production for Efficient Bulk Heterojunction Organic Solar Cells.

PubMed

Pirotte, Geert; Kesters, Jurgen; Verstappen, Pieter; Govaerts, Sanne; Manca, Jean; Lutsen, Laurence; Vanderzande, Dirk; Maes, Wouter

2015-10-12

Organic photovoltaics (OPV) have attracted great interest as a solar cell technology with appealing mechanical, aesthetical, and economies-of-scale features. To drive OPV toward economic viability, low-cost, large-scale module production has to be realized in combination with increased top-quality material availability and minimal batch-to-batch variation. To this extent, continuous flow chemistry can serve as a powerful tool. In this contribution, a flow protocol is optimized for the high performance benzodithiophene-thienopyrroledione copolymer PBDTTPD and the material quality is probed through systematic solar-cell evaluation. A stepwise approach is adopted to turn the batch process into a reproducible and scalable continuous flow procedure. Solar cell devices fabricated using the obtained polymer batches deliver an average power conversion efficiency of 7.2 %. Upon incorporation of an ionic polythiophene-based cathodic interlayer, the photovoltaic performance could be enhanced to a maximum efficiency of 9.1 %. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Production of black holes and their angular momentum distribution in models with split fermions

NASA Astrophysics Data System (ADS)

Dai, De-Chang; Starkman, Glenn D.; Stojkovic, Dejan

2006-05-01

In models with TeV-scale gravity it is expected that mini black holes will be produced in near-future accelerators. On the other hand, TeV-scale gravity is plagued with many problems like fast proton decay, unacceptably large n-n¯ oscillations, flavor changing neutral currents, large mixing between leptons, etc. Most of these problems can be solved if different fermions are localized at different points in the extra dimensions. We study the cross section for the production of black holes and their angular momentum distribution in these models with “split” fermions. We find that, for a fixed value of the fundamental mass scale, the total production cross section is reduced compared with models where all the fermions are localized at the same point in the extra dimensions. Fermion splitting also implies that the bulk component of the black hole angular momentum must be taken into account in studies of the black hole decay via Hawking radiation.

Assessing the importance of internal tide scattering in the deep ocean

NASA Astrophysics Data System (ADS)

Haji, Maha; Peacock, Thomas; Carter, Glenn; Johnston, T. M. Shaun

2014-11-01

Tides are one of the main sources of energy input to the deep ocean, and the pathways of energy transfer from barotropic tides to turbulent mixing scales via internal tides are not well understood. Large-scale (low-mode) internal tides account for the bulk of energy extracted from barotropic tides and have been observed to propagate over 1000 km from their generation sites. We seek to examine the fate of these large-scale internal tides and the processes by which their energy is transferred, or ``scattered,'' to small-scale (high-mode) internal tides, which dissipate locally and are responsible for internal tide driven mixing. The EXperiment on Internal Tide Scattering (EXITS) field study conducted in 2010-2011 sought to examine the role of topographic scattering at the Line Islands Ridge. The scattering process was examined via data from three moorings equipped with moored profilers, spanning total depths of 3000--5000 m. The results of our field data analysis are rationalized via comparison to data from two- and three-dimensional numerical models and a two-dimensional analytical model based on Green function theory.

Energy saving achieved by limited filamentous bulking sludge under low dissolved oxygen.

PubMed

Guo, Jian-Hua; Peng, Yong-Zhen; Peng, Cheng-Yao; Wang, Shu-Ying; Chen, Ying; Huang, Hui-Jun; Sun, Zhi-Rong

2010-02-01

Limited filamentous bulking caused by low dissolved oxygen (DO) was proposed to establish a low energy consumption wastewater treatment system. This method for energy saving was derived from two full-scale field observations, which showed pollutants removal would be enhanced and energy consumption could be reduced by at least 10% using limited filamentous bulking. Furthermore, preliminary investigation including the abundance evaluation and the identification of filamentous bacteria demonstrated that the limited filamentous bulking could be repeated steadily in a lab-scale anoxic-oxic reactor fed with domestic wastewater. The sludge loss did not occur in the secondary clarifier, while COD and total nitrogen removal efficiencies were improved by controlling DO for optimal filamentous bacterial population. Suspended solids in effluent were negligible and turbidity was lower than 2 NTU, which were distinctly lower than those under no bulking. Theoretical and experimental results indicated the aeration consumption could be saved by the application of limited filamentous bulking.

Three-dimensional carbon nanotubes for high capacity lithium-ion batteries

NASA Astrophysics Data System (ADS)

Kang, Chiwon; Patel, Mumukshu; Rangasamy, Baskaran; Jung, Kyu-Nam; Xia, Changlei; Shi, Sheldon; Choi, Wonbong

2015-12-01

Carbon nanotubes (CNTs) have been considered as a potential anode material for next generation Lithium-ion batteries (LIBs) due to their high conductivity, flexibility, surface area, and lithium-ion insertion ability. However, the low mass loading and bulk density of carbon nanomaterials hinder their use in large-scale energy storage because their high specific capacity may not scale up linearly with the thickness of the electrode. To address this issue, a novel three-dimensional (3D) architecture is rationally designed by stacking layers of free-standing CNTs with the increased areal density to 34.9 mg cm-2, which is around three-times higher than that of the state-of-the-art graphitic anodes. Furthermore, a thermal compression process renders the bulk density of the multi-stacked 3D CNTs to be increased by 1.85 g cm-3, which yields an excellent volumetric capacity of 465 mAh cm-3 at 0.5C. Our proposed strategy involving the stacking of 3D CNT based layers and post-thermal compression provides a powerful platform for the utilization of carbon nanomaterials in the advanced LIB technology.

Unsteady Crystal Growth Due to Step-Bunch Cascading

NASA Technical Reports Server (NTRS)

Vekilov, Peter G.; Lin, Hong; Rosenberger, Franz

1997-01-01

Based on our experimental findings of growth rate fluctuations during the crystallization of the protein lysozym, we have developed a numerical model that combines diffusion in the bulk of a solution with diffusive transport to microscopic growth steps that propagate on a finite crystal facet. Nonlinearities in layer growth kinetics arising from step interaction by bulk and surface diffusion, and from step generation by surface nucleation, are taken into account. On evaluation of the model with properties characteristic for the solute transport, and the generation and propagation of steps in the lysozyme system, growth rate fluctuations of the same magnitude and characteristic time, as in the experiments, are obtained. The fluctuation time scale is large compared to that of step generation. Variations of the governing parameters of the model reveal that both the nonlinearity in step kinetics and mixed transport-kinetics control of the crystallization process are necessary conditions for the fluctuations. On a microscopic scale, the fluctuations are associated with a morphological instability of the vicinal face, in which a step bunch triggers a cascade of new step bunches through the microscopic interfacial supersaturation distribution.

Energy saving processes for nitrogen removal in organic wastewater from food processing industries in Thailand.

PubMed

Johansen, N H; Suksawad, N; Balslev, P

2004-01-01

Nitrogen removal from organic wastewater is becoming a demand in developed communities. The use of nitrite as intermediate in the treatment of wastewater has been largely ignored, but is actually a relevant energy saving process compared to conventional nitrification/denitrification using nitrate as intermediate. Full-scale results and pilot-scale results using this process are presented. The process needs some additional process considerations and process control to be utilized. Especially under tropical conditions the nitritation process will round easily, and it must be expected that many AS treatment plants in the food industry already produce NO2-N. This uncontrolled nitrogen conversion can be the main cause for sludge bulking problems. It is expected that sludge bulking problems in many cases can be solved just by changing the process control in order to run a more consequent nitritation. Theoretically this process will decrease the oxygen consumption for oxidation by 25% and the use of carbon source for the reduction will be decreased by 40% compared to the conventional process.

Enhanced noise at high bias in atomic-scale Au break junctions

PubMed Central

Chen, Ruoyu; Wheeler, Patrick J.; Di Ventra, M.; Natelson, D.

2014-01-01

Heating in nanoscale systems driven out of equilibrium is of fundamental importance, has ramifications for technological applications, and is a challenge to characterize experimentally. Prior experiments using nanoscale junctions have largely focused on heating of ionic degrees of freedom, while heating of the electrons has been mostly neglected. We report measurements in atomic-scale Au break junctions, in which the bias-driven component of the current noise is used as a probe of the electronic distribution. At low biases (<150 mV) the noise is consistent with expectations of shot noise at a fixed electronic temperature. At higher biases, a nonlinear dependence of the noise power is observed. We consider candidate mechanisms for this increase, including flicker noise (due to ionic motion), heating of the bulk electrodes, nonequilibrium electron-phonon effects, and local heating of the electronic distribution impinging on the ballistic junction. We find that flicker noise and bulk heating are quantitatively unlikely to explain the observations. We discuss the implications of these observations for other nanoscale systems, and experimental tests to distinguish vibrational and electron interaction mechanisms for the enhanced noise. PMID:24573177

Fine-tuning with brane-localized flux in 6D supergravity

NASA Astrophysics Data System (ADS)

Niedermann, Florian; Schneider, Robert

2016-02-01

There are claims in the literature that the cosmological constant problem could be solved in a braneworld model with two large (micron-sized) supersymmetric extra dimensions. The mechanism relies on two basic ingredients: first, the cosmological constant only curves the compact bulk geometry into a rugby shape while the 4D curvature stays flat. Second, a brane-localized flux term is introduced in order to circumvent Weinberg's fine-tuning argument, which otherwise enters here through a backdoor via the flux quantization condition. In this paper, we show that the latter mechanism does not work in the way it was designed: the only localized flux coupling that guarantees a flat on-brane geometry is one which preserves the scale invariance of the bulk theory. Consequently, Weinberg's argument applies, making a fine-tuning necessary again. The only remaining window of opportunity lies within scale invariance breaking brane couplings, for which the tuning could be avoided. Whether the corresponding 4D curvature could be kept under control and in agreement with the observed value will be answered in our companion paper [1].

Constraining the effects of permeability uncertainty for geologic CO2 sequestration in a basalt reservoir

NASA Astrophysics Data System (ADS)

Jayne, R., Jr.; Pollyea, R.

2016-12-01

Carbon capture and sequestration (CCS) in geologic reservoirs is one strategy for reducing anthropogenic CO2 emissions from large-scale point-source emitters. Recent developments at the CarbFix CCS pilot in Iceland have shown that basalt reservoirs are highly effective for permanent mineral trapping on the basis of CO2-water-rock interactions, which result in the formation of carbonates minerals. In order to advance our understanding of basalt sequestration in large igneous provinces, this research uses numerical simulation to evaluate the feasibility of industrial-scale CO2 injections in the Columbia River Basalt Group (CRBG). Although bulk reservoir properties are well constrained on the basis of field and laboratory testing from the Wallula Basalt Sequestration Pilot Project, there remains significant uncertainty in the spatial distribution of permeability at the scale of individual basalt flows. Geostatistical analysis of hydrologic data from 540 wells illustrates that CRBG reservoirs are reasonably modeled as layered heterogeneous systems on the basis of basalt flow morphology; however, the regional dataset is insufficient to constrain permeability variability at the scale of an individual basalt flow. As a result, permeability distribution for this modeling study is established by centering the lognormal permeability distribution in the regional dataset over the bulk permeability measured at Wallula site, which results in a spatially random permeability distribution within the target reservoir. In order to quantify the effects of this permeability uncertainty, CO2 injections are simulated within 50 equally probable synthetic reservoir domains. Each model domain comprises three-dimensional geometry with 530,000 grid blocks, and fracture-matrix interaction is simulated as interacting continua for the two low permeability layers (flow interiors) bounding the injection zone. Results from this research illustrate that permeability uncertainty at the scale of individual basalt flows may significantly impact both injection pressure accumulation and CO2 distribution.

3D ion-scale dynamics of BBFs and their associated emissions in Earth's magnetotail using 3D hybrid simulations and MMS multi-spacecraft observations

NASA Astrophysics Data System (ADS)

Breuillard, H.; Aunai, N.; Le Contel, O.; Catapano, F.; Alexandrova, A.; Retino, A.; Cozzani, G.; Gershman, D. J.; Giles, B. L.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Strangeway, R. J.; Russell, C. T.; Magnes, W.; Plaschke, F.; Nakamura, R.; Fuselier, S. A.; Turner, D. L.; Schwartz, S. J.; Torbert, R. B.; Burch, J.

2017-12-01

Transient and localized jets of hot plasma, also known as Bursty Bulk Flows (BBFs), play a crucial role in Earth's magnetotail dynamics because the energy input from the solar wind is partly dissipated in their vicinity, notably in their embedded dipolarization front (DF). This dissipation is in the form of strong low-frequency waves that can heat and accelerate energetic particles up to the high-latitude plasma sheet. The ion-scale dynamics of BBFs have been revealed by the Cluster and THEMIS multi-spacecraft missions. However, the dynamics of BBF propagation in the magnetotail are still under debate due to instrumental limitations and spacecraft separation distances, as well as simulation limitations. The NASA/MMS fleet, which features unprecedented high time resolution instruments and four spacecraft separated by kinetic-scale distances, has also shown recently that the DF normal dynamics and its associated emissions are below the ion gyroradius scale in this region. Large variations in the dawn-dusk direction were also observed. However, most of large-scale simulations are using the MHD approach and are assumed 2D in the XZ plane. Thus, in this study we take advantage of both multi-spacecraft observations by MMS and large-scale 3D hybrid simulations to investigate the 3D dynamics of BBFs and their associated emissions at ion-scale in Earth's magnetotail, and their impact on particle heating and acceleration.

Exploring the Utilization of Low-Pressure, Piston-Cylinder Experiments to Determine the Bulk Compositions of Finite, Precious Materials

NASA Astrophysics Data System (ADS)

Vander Kaaden, K. E.; McCubbin, F. M.; Harrington, A.

2017-12-01

Determining the bulk composition of precious materials with a finite mass (e.g., meteorite samples) is extremely important in the fields of Earth and Planetary Science. From meteorite studies we are able to place constraints on large scale planetary processes like global differentiation and subsequent volcanism, as well as smaller scale processes like crystallization in a magma chamber or sedimentary compaction at the surface. However, with meteorite samples in particular, far too often we are limited by how precious the sample is as well as its limited mass. In this study, we have utilized aliquots of samples previously studied for toxicological hazards [1] including both the fresh samples (lunar mare basalt NWA 4734, lunar regolith breccia NWA 7611, martian basalt Tissint, martian regolith breccia NWA 7034, a vestian basalt Berthoud, a vestian regolith breccia NWA 2060, and a terrestrial mid-ocean ridge basalt (MORB)), and those that underwent iron leaching (Tissint, NWA 7034, NWA 4734, MORB). With these small masses of material, we performed low pressure ( 0.75 GPa), high temperature (>1600°C) melting experiments. Each sample was analyzed using a JEOL 8530F electron microprobe to determine the bulk composition of the materials that were previously examined in [1]. When available, the results of our microprobe data were compared with bulk rock compositions in the literature. The results of this study show that with this technique, only 50 mg of sample is required to accurately determine the bulk composition of the materials of interest. [1] Harrington, A.D., McCubbin, F.M., Kaur, J., Smirnov, A., Galdanes, K., Schoonen, M.A.A., Chen, L.C., Tsirka, S.E., and Gordon, T. (2017) Pulmonary inflammatory responses to acute meteroite dust exposures - Implications for human space exploration. 48th Lunar and Planetary Science Conference, The Woodlands, TX, #2922.

The mosaic structure of plasma bulk flows in the Earth's magnetotail

NASA Technical Reports Server (NTRS)

Ashour-Abdalla, M.; Richard, R. L.; Zelenyi, L. M.; Peroomian, V.; Bosqued, J. M.

1995-01-01

Moments of plasma distributions observed in the magnetotail vary with different time scales. In this paper we attempt to explain the observed variability on intermediate timescales of approximately 10-20 min that result from the simultaneous energization and spatial structuring of solar wind plasma in the distant magnetotail. These processes stimulate the formation of a system of spatially disjointed. highly accelerated filaments (beamlets) in the tail. We use the results from large-scale kinetic modeling of magnetotail formation from a plasma mantle source to calculate moments of ion distribution functions throughout the tail. Statistical restrictions related to the limited number of particles in our system naturally reduce the spatial resolution of our results, but we show that our model is valid on intermediate spatial scales Delta(x) x Delta(z) equal to approximately 1 R(sub E) x 1000 km. For these spatial scales the resulting pattern, which resembles a mosaic, appears to be quite variable. The complexity of the pattern is related to the spatial interference between beamlets accelerated at various locations within the distant tail which mirror in the strong near-Earth magnetic field. Global motion of the magnetotail results in the displacement of spacecraft with respect to this mosaic pattern and can produce variations in all of the moments (especially the x-component of the bulk velocity) on intermediate timescales. The results obtained enable us to view the magnetotail plasma as consisting of two different populations: a tailward-Earthward system of highly accelerated beamlets interfering with each other, and an energized quasithermal population which gradually builds as the Earth is approached. In the near-Earth tail, these populations merge into a hot quasi-isotropic ion population typical of the near-Earth plasma sheet. The transformation of plasma sheet boundary layer (PSBL) beam energy into central plasma sheet (CPS) quasi-thermal energy occurs in the absence of collisions or noise. This paper also clarifies the relationship between the global scale where an MHD description might be appropriate and the lower intermediate scales where MHD fails and large-scale kinetic theory should be used.

NASA Out-of-Autoclave Process Technology Development

NASA Technical Reports Server (NTRS)

Johnston, Norman, J.; Clinton, R. G., Jr.; McMahon, William M.

2000-01-01

Polymer matrix composites (PMCS) will play a significant role in the construction of large reusable launch vehicles (RLVs), mankind's future major access to low earth orbit and the international space station. PMCs are lightweight and offer attractive economies of scale and automated fabrication methodology. Fabrication of large RLV structures will require non-autoclave methods which have yet to be matured including (1) thermoplastic forming: heated head robotic tape placement, sheet extrusion, pultrusion, molding and forming; (2) electron beam curing: bulk and ply-by-ply automated placement; (3) RTM and VARTM. Research sponsored by NASA in industrial and NASA laboratories on automated placement techniques involving the first 2 categories will be presented.

Probing aerosol indirect effect on deep convection using idealized cloud-resolving simulations with parameterized large-scale dynamics.

NASA Astrophysics Data System (ADS)

Anber, U.; Wang, S.; Gentine, P.; Jensen, M. P.

2017-12-01

A framework is introduced to investigate the indirect impact of aerosol loading on tropical deep convection using 3-dimentional idealized cloud-system resolving simulations with coupled large-scale circulation. The large scale dynamics is parameterized using a spectral weak temperature gradient approximation that utilizes the dominant balance in the tropics between adiabatic cooling and diabatic heating. Aerosol loading effect is examined by varying the number concentration of nuclei (CCN) to form cloud droplets in the bulk microphysics scheme over a wide range from 30 to 5000 without including any radiative effect as the radiative cooling is prescribed at a constant rate, to isolate the microphysical effect. Increasing aerosol number concentration causes mean precipitation to decrease monotonically, despite the increase in cloud condensates. Such reduction in precipitation efficiency is attributed to reduction in the surface enthalpy fluxes, and not to the divergent circulation, as the gross moist stability remains unchanged. We drive a simple scaling argument based on the moist static energy budget, that enables a direct estimation of changes in precipitation given known changes in surfaces enthalpy fluxes and the constant gross moist stability. The impact on cloud hydrometers and microphysical properties is also examined and is consistent with the macro-physical picture.

Hybrid Markov-mass action law model for cell activation by rare binding events: Application to calcium induced vesicular release at neuronal synapses.

PubMed

Guerrier, Claire; Holcman, David

2016-10-18

Binding of molecules, ions or proteins to small target sites is a generic step of cell activation. This process relies on rare stochastic events where a particle located in a large bulk has to find small and often hidden targets. We present here a hybrid discrete-continuum model that takes into account a stochastic regime governed by rare events and a continuous regime in the bulk. The rare discrete binding events are modeled by a Markov chain for the encounter of small targets by few Brownian particles, for which the arrival time is Poissonian. The large ensemble of particles is described by mass action laws. We use this novel model to predict the time distribution of vesicular release at neuronal synapses. Vesicular release is triggered by the binding of few calcium ions that can originate either from the synaptic bulk or from the entry through calcium channels. We report here that the distribution of release time is bimodal although it is triggered by a single fast action potential. While the first peak follows a stimulation, the second corresponds to the random arrival over much longer time of ions located in the synaptic terminal to small binding vesicular targets. To conclude, the present multiscale stochastic modeling approach allows studying cellular events based on integrating discrete molecular events over several time scales.

Perspective: Aerosol microphysics: From molecules to the chemical physics of aerosols

NASA Astrophysics Data System (ADS)

Bzdek, Bryan R.; Reid, Jonathan P.

2017-12-01

Aerosols are found in a wide diversity of contexts and applications, including the atmosphere, pharmaceutics, and industry. Aerosols are dispersions of particles in a gas, and the coupling of the two phases results in highly dynamic systems where chemical and physical properties like size, composition, phase, and refractive index change rapidly in response to environmental perturbations. Aerosol particles span a wide range of sizes from 1 nm to tens of micrometres or from small molecular clusters that may more closely resemble gas phase molecules to large particles that can have similar qualities to bulk materials. However, even large particles with finite volumes exhibit distinct properties from the bulk condensed phase, due in part to their higher surface-to-volume ratio and their ability to easily access supersaturated solute states inaccessible in the bulk. Aerosols represent a major challenge for study because of the facile coupling between the particle and gas, the small amounts of sample available for analysis, and the sheer breadth of operative processes. Time scales of aerosol processes can be as short as nanoseconds or as long as years. Despite their very different impacts and applications, fundamental chemical physics processes serve as a common theme that underpins our understanding of aerosols. This perspective article discusses challenges in the study of aerosols and highlights recent chemical physics advancements that have enabled improved understanding of these complex systems.

Dynamics of a Room Temperature Ionic Liquid in Supported Ionic Liquid Membranes vs the Bulk Liquid: 2D IR and Polarized IR Pump-Probe Experiments.

PubMed

Shin, Jae Yoon; Yamada, Steven A; Fayer, Michael D

2017-01-11

Supported ionic liquid membranes (SILMs) are membranes that have ionic liquids impregnated in their pores. SILMs have been proposed for advanced carbon capture materials. Two-dimensional infrared (2D IR) and polarization selective IR pump-probe (PSPP) techniques were used to investigate the dynamics of reorientation and spectral diffusion of the linear triatomic anion, SeCN - , in poly(ether sulfone) (PES) membranes and room-temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf 2 ). The dynamics in the bulk EmimNTf 2 were compared to its dynamics in the SILM samples. Two PES membranes, PES200 and PES30, have pores with average sizes, ∼300 nm and ∼100 nm, respectively. Despite the relatively large pore sizes, the measurements reveal that the reorientation of SeCN - and the RTIL structural fluctuations are substantially slower in the SILMs than in the bulk liquid. The complete orientational randomization, slows from 136 ps in the bulk to 513 ps in the PES30. 2D IR measurements yield three time scales for structural spectral diffusion (SSD), that is, the time evolution of the liquid structure. The slowest decay constant increases from 140 ps in the bulk to 504 ps in the PES200 and increases further to 1660 ps in the PES30. The results suggest that changes at the interface propagate out and influence the RTIL structural dynamics even more than a hundred nanometers from the polymer surface. The differences between the IL dynamics in the bulk and in the membranes suggest that studies of bulk RTIL properties may be poor guides to their use in SILMs in carbon capture applications.

Satellite traces: An ionogram signature for large-scale wave structure and a precursor for equatorial spread F

NASA Astrophysics Data System (ADS)

Tsunoda, Roland T.

2008-10-01

Although the source that controls day-to-day variability in the occurrence of equatorial plasma structure (i.e., equatorial spread F, or ESF) remains to be identified, progress is being made. There is evidence that the appearance of large-scale wave structure (LSWS) in the bottomside F layer, around the time of its post-sunset rise (PSSR), is a more-direct precursor of ESF than the PSSR itself. The bulk of the evidence, however, is in the form of ``satellite'' F traces in ionograms, which may be viewed as less than convincing, because these signatures have not been shown to be causally related to LSWS. In this paper, incoherent-scatter radar and ionosonde data, both collected on 24 July 1979 from the Kwajalein atoll, Marshall Islands, are used to show that this is indeed the case.

Synchrotron radiation x-ray topography and defect selective etching analysis of threading dislocations in GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sintonen, Sakari, E-mail: sakari.sintonen@aalto.fi; Suihkonen, Sami; Jussila, Henri

2014-08-28

The crystal quality of bulk GaN crystals is continuously improving due to advances in GaN growth techniques. Defect characterization of the GaN substrates by conventional methods is impeded by the very low dislocation density and a large scale defect analysis method is needed. White beam synchrotron radiation x-ray topography (SR-XRT) is a rapid and non-destructive technique for dislocation analysis on a large scale. In this study, the defect structure of an ammonothermal c-plane GaN substrate was recorded using SR-XRT and the image contrast caused by the dislocation induced microstrain was simulated. The simulations and experimental observations agree excellently and themore » SR-XRT image contrasts of mixed and screw dislocations were determined. Apart from a few exceptions, defect selective etching measurements were shown to correspond one to one with the SR-XRT results.« less

Delignified and Densified Cellulose Bulk Materials with Excellent Tensile Properties for Sustainable Engineering.

PubMed

Frey, Marion; Widner, Daniel; Segmehl, Jana S; Casdorff, Kirstin; Keplinger, Tobias; Burgert, Ingo

2018-02-07

Today's materials research aims at excellent mechanical performance in combination with advanced functionality. In this regard, great progress has been made in tailoring the materials by assembly processes in bottom-up approaches. In the field of wood-derived materials, nanocellulose research has gained increasing attention, and materials with advanced properties were developed. However, there are still unresolved issues concerning upscaling for large-scale applications. Alternatively, the sophisticated hierarchical scaffold of wood can be utilized in a top-down approach to upscale functionalization, and one can profit at the same time from its renewable nature, CO 2 storing capacity, light weight, and good mechanical performance. Nevertheless, for bulk wood materials, a wider multipurpose industrial use is so far impeded by concerns regarding durability, natural heterogeneity as well as limitations in terms of functionalization, processing, and shaping. Here, we present a novel cellulose bulk material concept based on delignification and densification of wood resulting in a high-performance material. A delignification process using hydrogen peroxide and acetic acid was optimized to delignify the entire bulk wooden blocks and to retain the highly beneficial structural directionality of wood. In a subsequent step, these cellulosic blocks were densified in a process combining compression and lateral shear to gain a very compact cellulosic material with entangled fibers while retaining unidirectional fiber orientation. The cellulose bulk materials obtained by different densification protocols were structurally, chemically, and mechanically characterized revealing superior tensile properties compared to native wood. Furthermore, after delignification, the cellulose bulk material can be easily formed into different shapes, and the delignification facilitates functionalization of the bioscaffold.

Three-dimensional hydrodynamic simulations of OMEGA implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; Campbell, E. M.; Epstein, R.; Forrest, C. J.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Marshall, F. J.; McCrory, R. L.; Regan, S. P.; Sangster, T. C.; Stoeckl, C.; Schmitt, A. J.; Obenschain, S.

2017-05-01

The effects of large-scale (with Legendre modes ≲ 10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets ( ˜10 to 20 μm), beam-power imbalance ( σrms˜10 %), and variations ( ˜5 %) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosion targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ˜1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh-Taylor growth.

Three-dimensional hydrodynamic simulations of OMEGA implosions

DOE PAGES

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; ...

2017-03-30

Here, the effects of large-scale (with Legendre modes ≲10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets (~10 to 20 μm), beam-power imbalance (σ rms ~ 10%), and variations (~5%) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosionmore » targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ~1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh–Taylor growth.« less

Three-dimensional hydrodynamic simulations of OMEGA implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.

Here, the effects of large-scale (with Legendre modes ≲10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets (~10 to 20 μm), beam-power imbalance (σ rms ~ 10%), and variations (~5%) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosionmore » targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ~1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh–Taylor growth.« less

Promising diphoton signals of the little radion at hadron colliders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davoudiasl, H.; McElmurry, T; Soni, A.

2010-12-28

In little Randall-Sundrum models, the bulk couplings of the radion to massless gauge fields can yield a greatly enhanced diphoton signal at hadron colliders. We examine the implications of the Tevatron data for the little radion and also show that the 7 TeV run at the Large Hadron Collider will have an impressive reach in this channel. The diphoton signal is crucial in the search for a light radion, or the dual dilaton, and can potentially probe the ultraviolet scale of the theory.

High Performance Piezoelectric Actuators and Wings for Nano Air Vehicles

DTIC Science & Technology

2012-08-26

we designed and fabricated the LionFly, a flapping wing prototype actuated by a PZT -5H bimorph actuator. Several LionFly prototypes were fabricated...in the literature, using PZT thin film actuators directly coupled to a 2.5 mm SiO2/Si3N4/T i-Au wing that produces large flapping angle at resonance...for larger scale mechanisms [17, 9]. For PAVs, linear electromagnetic ac- tuation [21] and bulk PZT bimorph actuators [8], and thin film PZT unimorph

Dual-Mode Adhesive Pad

NASA Technical Reports Server (NTRS)

Hartz, Leslie

1994-01-01

Tool helps worker grip and move along large, smooth structure with no handgrips or footholds. Adheres to surface but easily released by actuating simple mechanism. Includes handle and segmented contact-adhesive pad. Bulk of pad made of soft plastic foam conforming to surface of structure. Each segment reinforced with rib. In sticking mode, ribs braced by side catches. In peeling mode, side catches retracted, and segmented adhesive pad loses its stiffness. Modified versions useful in inspecting hulls of ships and scaling walls in rescue operations.

Scaling laws and bulk-boundary decoupling in heat flow.

PubMed

del Pozo, Jesús J; Garrido, Pedro L; Hurtado, Pablo I

2015-03-01

When driven out of equilibrium by a temperature gradient, fluids respond by developing a nontrivial, inhomogeneous structure according to the governing macroscopic laws. Here we show that such structure obeys strikingly simple scaling laws arbitrarily far from equilibrium, provided that both macroscopic local equilibrium and Fourier's law hold. Extensive simulations of hard disk fluids confirm the scaling laws even under strong temperature gradients, implying that Fourier's law remains valid in this highly nonlinear regime, with putative corrections absorbed into a nonlinear conductivity functional. In addition, our results show that the scaling laws are robust in the presence of strong finite-size effects, hinting at a subtle bulk-boundary decoupling mechanism which enforces the macroscopic laws on the bulk of the finite-sized fluid. This allows one to measure the marginal anomaly of the heat conductivity predicted for hard disks.

Porous 3D graphene-based bulk materials with exceptional high surface area and excellent conductivity for supercapacitors

PubMed Central

Zhang, Long; Zhang, Fan; Yang, Xi; Long, Guankui; Wu, Yingpeng; Zhang, Tengfei; Leng, Kai; Huang, Yi; Ma, Yanfeng; Yu, Ao; Chen, Yongsheng

2013-01-01

Until now, few sp2 carbon materials simultaneously exhibit superior performance for specific surface area (SSA) and electrical conductivity at bulk state. Thus, it is extremely important to make such materials at bulk scale with those two outstanding properties combined together. Here, we present a simple and green but very efficient approach using two standard and simple industry steps to make such three-dimensional graphene-based porous materials at the bulk scale, with ultrahigh SSA (3523 m2/g) and excellent bulk conductivity. We conclude that these materials consist of mainly defected/wrinkled single layer graphene sheets in the dimensional size of a few nanometers, with at least some covalent bond between each other. The outstanding properties of these materials are demonstrated by their superior supercapacitor performance in ionic liquid with specific capacitance and energy density of 231 F/g and 98 Wh/kg, respectively, so far the best reported capacitance performance for all bulk carbon materials. PMID:23474952

Roll-to-Roll printed large-area all-polymer solar cells with 5% efficiency based on a low crystallinity conjugated polymer blend

NASA Astrophysics Data System (ADS)

Gu, Xiaodan; Zhou, Yan; Gu, Kevin; Kurosawa, Tadanori; Yan, Hongping; Wang, Cheng; Toney, Micheal; Bao, Zhenan

The challenge of continuous printing in high efficiency large-area organic solar cells is a key limiting factor for their widespread adoption. We present a materials design concept for achieving large-area, solution coated all-polymer bulk heterojunction (BHJ) solar cells with stable phase separation morphology between the donor and acceptor. The key concept lies in inhibiting strong crystallization of donor and acceptor polymers, thus forming intermixed, low crystallinity and mostly amorphous blends. Based on experiments using donors and acceptors with different degree of crystallinity, our results showed that microphase separated donor and acceptor domain sizes are inversely proportional to the crystallinity of the conjugated polymers. This methodology of using low crystallinity donors and acceptors has the added benefit of forming a consistent and robust morphology that is insensitive to different processing conditions, allowing one to easily scale up the printing process from a small scale solution shearing coater to a large-scale continuous roll-to-roll (R2R) printer. We were able to continuously roll-to-roll slot die print large area all-polymer solar cells with power conversion efficiencies of 5%, with combined cell area up to 10 cm2. This is among the highest efficiencies realized with R2R coated active layer organic materials on flexible substrate. DOE BRIDGE sunshot program. Office of Naval Research.

Roll-to-Roll Printed Large-Area All-Polymer Solar Cells with 5% Efficiency Based on a Low Crystallinity Conjugated Polymer Blend

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Xiaodan; Zhou, Yan; Gu, Kevin

The challenge of continuous printing in high-efficiency large-area organic solar cells is a key limiting factor for their widespread adoption. We present a materials design concept for achieving large-area, solution-coated all-polymer bulk heterojunction solar cells with stable phase separation morphology between the donor and acceptor. The key concept lies in inhibiting strong crystallization of donor and acceptor polymers, thus forming intermixed, low crystallinity, and mostly amorphous blends. Based on experiments using donors and acceptors with different degree of crystallinity, the results show that microphase separated donor and acceptor domain sizes are inversely proportional to the crystallinity of the conjugated polymers.more » This particular methodology of using low crystallinity donors and acceptors has the added benefit of forming a consistent and robust morphology that is insensitive to different processing conditions, allowing one to easily scale up the printing process from a small-scale solution shearing coater to a large-scale continuous roll-to-roll (R2R) printer. Large-area all-polymer solar cells are continuously roll-to-roll slot die printed with power conversion efficiencies of 5%, with combined cell area up to 10 cm 2. This is among the highest efficiencies realized with R2R-coated active layer organic materials on flexible substrate.« less

Roll-to-Roll Printed Large-Area All-Polymer Solar Cells with 5% Efficiency Based on a Low Crystallinity Conjugated Polymer Blend

DOE PAGES

Gu, Xiaodan; Zhou, Yan; Gu, Kevin; ...

2017-03-07

The challenge of continuous printing in high-efficiency large-area organic solar cells is a key limiting factor for their widespread adoption. We present a materials design concept for achieving large-area, solution-coated all-polymer bulk heterojunction solar cells with stable phase separation morphology between the donor and acceptor. The key concept lies in inhibiting strong crystallization of donor and acceptor polymers, thus forming intermixed, low crystallinity, and mostly amorphous blends. Based on experiments using donors and acceptors with different degree of crystallinity, the results show that microphase separated donor and acceptor domain sizes are inversely proportional to the crystallinity of the conjugated polymers.more » This particular methodology of using low crystallinity donors and acceptors has the added benefit of forming a consistent and robust morphology that is insensitive to different processing conditions, allowing one to easily scale up the printing process from a small-scale solution shearing coater to a large-scale continuous roll-to-roll (R2R) printer. Large-area all-polymer solar cells are continuously roll-to-roll slot die printed with power conversion efficiencies of 5%, with combined cell area up to 10 cm 2. This is among the highest efficiencies realized with R2R-coated active layer organic materials on flexible substrate.« less

Large Scale Brownian Dynamics of Confined Suspensions of Rigid Particles

NASA Astrophysics Data System (ADS)

Donev, Aleksandar; Sprinkle, Brennan; Balboa, Florencio; Patankar, Neelesh

2017-11-01

We introduce new numerical methods for simulating the dynamics of passive and active Brownian colloidal suspensions of particles of arbitrary shape sedimented near a bottom wall. The methods also apply for periodic (bulk) suspensions. Our methods scale linearly in the number of particles, and enable previously unprecedented simulations of tens to hundreds of thousands of particles. We demonstrate the accuracy and efficiency of our methods on a suspension of boomerang-shaped colloids. We also model recent experiments on active dynamics of uniform suspensions of spherical microrollers. This work was supported in part by the National Science Foundation under award DMS-1418706, and by the U.S. Department of Energy under award DE-SC0008271.

Spatial distribution of soil moisture obtained from gravimetric and TDR methods for SMOS validation, at the Polesie test site SVRT 3275, in Poland

NASA Astrophysics Data System (ADS)

Usowicz, B.; Marczewski, W.; Lipiec, J.; Usowicz, J. B.; Sokolowska, Z.; Dabkowska-Naskret, H.; Hajnos, M.; Lukowski, M. I.

2009-04-01

The purpose is obtaining trustful ground based measurement data of SM (Soil Moisture) for validating SMOS, respectively to spatial and temporal distribution and variations. A use of Time Domain Reflectometric (TDR) method is fast, simple and less destructive, to the soil matter, than a usual standard gravimetric method. TDR tools operate efficiently, enable nearly instant measurements, and allow on collecting many measurements from numerous sites, even when operated manually in short time intervals. The method enables also very frequent sampling of SM at few selected fixed sites, when long terms of temporal variations are needed. In effect one obtains reasonably large data base for determining spatial and temporal distributions of SM. The study is devoted to determining a plan on collecting TDR data, in the scales of small and large field areas, and checking their relevance to those available from gravimetric methods. Finally, the ground based SM distributions are needed for validating other SM distributions, available remotely in larger scales, from the satellite data of ENVISAT-ASAR, and from SMOS (Soil Moisture and Ocean Salinity Mission) when it becomes operational. The ground based evaluations are served mainly by geo-statistical analysis. The space borne estimations are retrieved by image processing and physical models, proper to relevant Remote Sensing (RS) instruments on the orbit. Finally, validation must engage again the geo-statistical evaluations, to assess the agreement between direct and remote sensing means, and provide a measure of trust for extending the limited scales of the ground based data, on concluding the agreement in scales proper to the satellite data. The study is focused mainly on trustful evaluating data from the ground, provided independently on satellite data sources. SM ground based data are collected permanently at 2 selected tests sites, and temporary in areas around the tests sites, in one day sessions, repeated several times per vegetation season. Permanent measurements are provided in profiles, down to 50 cm below surface. Temporary SM measurements are collected by hand held TDR (FOM/mts type, Easy Test Ltd., Lublin, Poland) from the top surface layer (1-6 cm), in a grid covering small and large areas, containing few hundred sites. The same places are served by collecting soil samples for the gravimetric analysis of SM, bulk density, other physical and textural characteristics. Sessions on measurement in large areas on the scale of community are repeated for separate days. The two methods used were compared with correlation coefficient, regression equation and differences of values. The spatial variability of soil moisture from gravimetric and TDR measurements were analyzed using geostatistical methods. The semivariogram parameters were determined and mathematical functions were fitted to empirically derived semivariograms. These functions were used for estimation of spatial distribution of soil moisture in cultivated fields by the kriging method. The results showed that spatial distribution patterns of topsoil soil moisture in the investigated areas obtained from TDR and gravimetric methods were in general similar to each other. The TDR soil moisture contents were dependent on bulk density and texture of soil. In areas with fine-textured soils of lower soil bulk densities (approximately below 1.35 Mg m^-3) we observed that TDR soil moisture and spatial differentiation were greater compared to those with gravimetric method. However at higher bulk densities the inverse was true. The spatial patterns were further modified in areas with domination of coarse-textured soils. Decrease of measurement points results in smoothing soil moisture pattern and at the same time in a greater estimation error. The TDR method can be useful tool for ground moisture measurements and validation of satellite data. The use of specific calibration or correction for soil bulk density and texture with respect to the reflectometric method is recommended. The study is a contribution to the project SWEX (AO-3275) and funded by the Polish Ministry of Science and Higher Education (in part by Grant No. N305 046 31/1707 and in part by Grant No. N305 107 32/3865).

Quality Assessment of Physical and Organoleptic Instant Corn Rice on Scale-Up Process

NASA Astrophysics Data System (ADS)

Kumalasari, R.; Ekafitri, R.; Indrianti, N.

2017-12-01

Development of instant corn rice product has been successfully conducted on a laboratory scale. Corn has high carbohydrate content but low in fiber. The addition of fiber in instant corn rice, intended to improve the functioning of the product, and replace fiber loss during the process. Scale up process of Instant corn rice required to increase the production capacity. Scale up was the process to get identic output on a larger scale based on predetermined production scale. This study aimed to assess the changes and differences in the quality of instant corn rice during scale up. Instant corn rice scale up was done on production capacity 3 kg, 4 kg and 5 kg. Results showed that scale up of instant corn rice producing products with rehydration ratio ranges between 514% - 570%, the absorption rate ranged between 414% - 470%, swelling rate ranging between 119% - 134%, bulk density ranged from 0.3661 to 0.4745 (g/ml) and porosity ranging between 30-37%. The physical quality of instant corn rice on scale up were stable from the ones at laboratory scale on swelling rate, rehydration ratio, and absorption rate but not stable on bulk density and porosity. Organoleptic qualities were stable at increased scale compared on a laboratory scale. Bulk density was higher than those at laboratory scale, and the porosity was lower than those at laboratory scale.

Evolution of the electrical resistivity anisotropy during saline tracer tests: insights from geoelectrical milli-fluidic experiments

NASA Astrophysics Data System (ADS)

Jougnot, D.; Jimenez-Martinez, J.; Legendre, R.; Le Borgne, T.; Meheust, Y.; Linde, N.

2017-12-01

The use of time-lapse electrical resistivity tomography has been largely developed in environmental studies to remotely monitor water saturation and contaminant plumes migration. However, subsurface heterogeneities, and corresponding preferential transport paths, yield a potentially large anisotropy in the electrical properties of the subsurface. In order to study this effect, we have used a newly developed geoelectrical milli-fluidic experimental set-up with a flow cell that contains a 2D porous medium consisting of a single layer of cylindrical solid grains. We performed saline tracer tests under full and partial water saturations in that cell by jointly injecting air and aqueous solutions with different salinities. The flow cell is equipped with four electrodes to measure the bulk electrical resistivity at the cell's scale. The spatial distribution of the water/air phases and the saline solute concentration field in the water phase are captured simultaneously with a high-resolution camera by combining a fluorescent tracer with the saline solute. These data are used to compute the longitudinal and transverse effective electrical resistivity numerically from the measured spatial distributions of the fluid phases and the salinity field. This approach is validated as the computed longitudinal effective resistivities are in good agreement with the laboratory measurements. The anisotropy in electrical resistivity is then inferred from the computed longitudinal and transverse effective resistivities. We find that the spatial distribution of saline tracer, and potentially air phase, drive temporal changes in the effective resistivity through preferential paths or barriers for electrical current at the pore scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical resistivity, especially for partially saturated conditions. Therefore, considering the electrical resistivity as a tensor could improve our understanding of transport properties from field-scale time-lapse ERT.

Formation of Apollo 16 impactites and the composition of late accreted material: Constraints from Os isotopes, highly siderophile elements and sulfur abundances

NASA Astrophysics Data System (ADS)

Gleißner, Philipp; Becker, Harry

2017-03-01

Fe-Ni metal-schreibersite-troilite intergrowths in Apollo 16 impact melt rocks and new highly siderophile element (HSE) and S abundance data indicate that millimeter-scale closed-system fractional crystallization processes during cooling of impactor-derived metal melt droplets in impact-melts are the main reason for compositional variations and strong differences in abundances and ratios of HSE in multiple aliquots from Apollo 16 impact melt rocks. Element ratios obtained from linear regression of such data are therefore prone to error, but weighted averages take into account full element budgets in the samples and thus represent a more accurate estimate of their impactor contributions. Modeling of solid metal-liquid metal partitioning in the Fe-Ni-S-P system and HSE patterns in impactites from different landing sites suggest that bulk compositions of ancient lunar impactites should be representative of impact melt compositions and that large-scale fractionation of the HSE by in situ segregation of solid metal or sulfide liquid in impact melt sheets most likely did not occur. The compositional record of lunar impactites indicates accretion of variable amounts of chondritic and non-chondritic impactor material and the mixing of these components during remelting of earlier ejecta deposits. The non-chondritic composition appears most prominently in some Apollo 16 impactites and is characterized by suprachondritic HSE/Ir ratios which increase from refractory to moderately volatile HSE and exhibit a characteristic enrichment of Ru relative to Pt. Large-scale fractional crystallization of solid metal from sulfur and phosphorous rich metallic melt with high P/S in planetesimal or embryo cores is currently the most likely process that may have produced these compositions. Similar materials or processes may have contributed to the HSE signature of the bulk silicate Earth (BSE).

On the evolution of flow topology in turbulent Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Dabbagh, F.; Trias, F. X.; Gorobets, A.; Oliva, A.

2016-11-01

Small-scale dynamics is the spirit of turbulence physics. It implicates many attributes of flow topology evolution, coherent structures, hairpin vorticity dynamics, and mechanism of the kinetic energy cascade. In this work, several dynamical aspects of the small-scale motions have been numerically studied in a framework of Rayleigh-Bénard convection (RBC). To do so, direct numerical simulations have been carried out at two Rayleigh numbers Ra = 108 and 1010, inside an air-filled rectangular cell of aspect ratio unity and π span-wise open-ended distance. As a main feature, the average rate of the invariants of the velocity gradient tensor (QG, RG) has displayed the so-called "teardrop" spiraling shape through the bulk region. Therein, the mean trajectories are swirling inwards revealing a periodic spin around the converging origin of a constant period that is found to be proportional to the plumes lifetime. This suggests that the thermal plumes participate in the coherent large-scale circulation and the turbulent wind created in the bulk. Particularly, it happens when the plumes elongate substantially to contribute to the large-scale eddies at the lower turbulent state. Supplementary small-scale properties, which are widely common in many turbulent flows have been observed in RBC. For example, the strong preferential alignment of vorticity with the intermediate eigenstrain vector, and the asymmetric alignment between vorticity and the vortex-stretching vector. It has been deduced that in a hard turbulent flow regime, local self-amplifications of straining regions aid in contracting the vorticity worms, and enhance the local interactions vorticity/strain to support the linear vortex-stretching contributions. On the other hand, the evolution of invariants pertained to the traceless part of velocity-times-temperature gradient tensor has also been considered in order to determine the role of thermals in the fine-scale dynamics. These new invariants show an incorporation of kinetic and thermal gradient dynamics that indicate directly the evolution and lifetime of thermal plume structures. By applying an identical approach, the rates of the new invariants have shown a symmetric cycling behaviour decaying towards two skew-symmetric converging origins at the lower Ra number. The trajectories near origins address the hot and cold coherent plumes that travel as an average large-scale heat flux in the sidewall vicinities, and denote a periodic spin period close to the plumes lifetime. At the hard turbulent case, the spiraling trajectories travel in shorter tracks to reveal the reduced lifetime of plumes under the dissipative and mixing effects. The turbulent background kinetic derivatives get self-amplified and the trajectories converge to a zero-valued origin indicating that there is no contribution from the plumes to the average coherent large scales of heat flux. These and other peculiar scrutinies on the small-scale motions in RBC have been enlightened, and may have a fruitful consequence on modelling approaches of buoyancy-driven turbulence.

Investigating the Complex Chemistry of Functional Energy Storage Systems: The Need for an Integrative, Multiscale (Molecular to Mesoscale) Perspective.

PubMed

Abraham, Alyson; Housel, Lisa M; Lininger, Christianna N; Bock, David C; Jou, Jeffrey; Wang, Feng; West, Alan C; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S

2016-06-22

Electric energy storage systems such as batteries can significantly impact society in a variety of ways, including facilitating the widespread deployment of portable electronic devices, enabling the use of renewable energy generation for local off grid situations and providing the basis of highly efficient power grids integrated with energy production, large stationary batteries, and the excess capacity from electric vehicles. A critical challenge for electric energy storage is understanding the basic science associated with the gap between the usable output of energy storage systems and their theoretical energy contents. The goal of overcoming this inefficiency is to achieve more useful work (w) and minimize the generation of waste heat (q). Minimization of inefficiency can be approached at the macro level, where bulk parameters are identified and manipulated, with optimization as an ultimate goal. However, such a strategy may not provide insight toward the complexities of electric energy storage, especially the inherent heterogeneity of ion and electron flux contributing to the local resistances at numerous interfaces found at several scale lengths within a battery. Thus, the ability to predict and ultimately tune these complex systems to specific applications, both current and future, demands not just parametrization at the bulk scale but rather specific experimentation and understanding over multiple length scales within the same battery system, from the molecular scale to the mesoscale. Herein, we provide a case study examining the insights and implications from multiscale investigations of a prospective battery material, Fe3O4.

The effect of sulfate concentration on (sub)millimeter-scale sulfide δ 34S in hypersaline cyanobacterial mats over the diurnal cycle

NASA Astrophysics Data System (ADS)

Fike, David A.; Finke, Niko; Zha, Jessica; Blake, Garrett; Hoehler, Tori M.; Orphan, Victoria J.

2009-10-01

Substantial isotopic fractionations are associated with many microbial sulfur metabolisms and measurements of the bulk δ 34S isotopic composition of sulfur species (predominantly sulfates and/or sulfides) have been a key component in developing our understanding of both modern and ancient biogeochemical cycling. However, the interpretations of bulk δ 34S measurements are often non-unique, making reconstructions of paleoenvironmental conditions or microbial ecology challenging. In particular, the link between the μm-scale microbial activity that generates isotopic signatures and their eventual preservation as a bulk rock value in the geologic record has remained elusive, in large part because of the difficulty of extracting sufficient material at small scales. Here we investigate the potential for small-scale (˜100 μm-1 cm) δ 34S variability to provide additional constraints for environmental and/or ecological reconstructions. We have investigated the impact of sulfate concentrations (0.2, 1, and 80 mM SO 4) on the δ 34S composition of hydrogen sulfide produced over the diurnal (day/night) cycle in cyanobacterial mats from Guerrero Negro, Baja California Sur, Mexico. Sulfide was captured as silver sulfide on the surface of a 2.5 cm metallic silver disk partially submerged beneath the mat surface. Subsequent analyses were conducted on a Cameca 7f-GEO secondary ion mass spectrometer (SIMS) to record spatial δ 34S variability within the mats under different environmental conditions. Isotope measurements were made in a 2-dimensional grid for each incubation, documenting both lateral and vertical isotopic variation within the mats. Typical grids consisted of ˜400-800 individual measurements covering a lateral distance of ˜1 mm and a vertical depth of ˜5-15 mm. There is a large isotopic enrichment (˜10-20‰) in the uppermost mm of sulfide in those mats where [SO 4] was non-limiting (field and lab incubations at 80 mM). This is attributed to rapid recycling of sulfur (elevated sulfate reduction rates and extensive sulfide oxidation) at and above the chemocline. This isotopic gradient is observed in both day and night enrichments and suggests that, despite the close physical association between cyanobacteria and select sulfate-reducing bacteria, photosynthetic forcing has no substantive impact on δ 34S in these cyanobacterial mats. Perhaps equally surprising, large, spatially-coherent δ 34S oscillations (˜20-30‰ over 1 mm) occurred at depths up to ˜1.5 cm below the mat surface. These gradients must arise in situ from differential microbial metabolic activity and fractionation during sulfide production at depth. Sulfate concentrations were the dominant control on the spatial variability of sulfide δ 34S. Decreased sulfate concentrations diminished both vertical and lateral δ 34S variability, suggesting that small-scale variations of δ 34S can be diagnostic for reconstructing past sulfate concentrations, even when original sulfate δ 34S is unknown.

Seals Research at Texas A/M University

NASA Technical Reports Server (NTRS)

Morrison, Gerald L.

1991-01-01

The Turbomachinery Laboratory at Texas A&M has been providing experimental data and computational codes for the design seals for many years. The program began with the development of a Halon based seal test rig. This facility provided information about the effective stiffness and damping in whirling seals. The Halon effectively simulated cryogenic fluids. Another test facility was developed (using air as the working fluid) where the stiffness and damping matrices can be determined. This data was used to develop bulk flow models of the seal's effect upon rotating machinery; in conjunction with this research, a bulk flow model for calculation of performance and rotordynamic coefficients of annular pressure seals of arbitrary non-uniform clearance for barotropic fluids such as LH2, LOX, LN2, and CH4 was developed. This program is very efficient (fast) and converges for very large eccentricities. Currently, work is being performed on a bulk flow analysis of the effects of the impeller-shroud interaction upon the stability of pumps. The data was used along with data from other researchers to develop an empirical leakage prediction code for MSFC. Presently, the flow field inside labyrinth and annular seals are being studied in detail. An advanced 3-D Doppler anemometer system is being used to measure the mean velocity and entire Reynolds stress tensor distribution throughout the seals. Concentric and statically eccentric seals were studied; presently, whirling seals are being studied. The data obtained are providing valuable information about the flow phenomena occurring inside the seals, as well as a data base for comparison with numerical predictions and for turbulence model development. A finite difference computer code was developed for solving the Reynolds averaged Navier Stokes equation inside labyrinth seals. A multi-scale k-epsilon turbulence model is currently being evaluated. A new seal geometry was designed and patented using a computer code. A large scale, 2-D seal flow visualization facility is also being developed.

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

NASA Astrophysics Data System (ADS)

Singh, C. P.; Srivastava, Milan

2018-03-01

In this work, we study a flat Friedmann-Robertson-Walker universe filled with dark matter and viscous new holographic dark energy. We present four possible solutions of the model depending on the choice of the viscous term. We obtain the evolution of the cosmological quantities such as scale factor, deceleration parameter and transition redshift to observe the effect of viscosity in the evolution. We also emphasis upon the two independent geometrical diagnostics for our model, namely the statefinder and the Om diagnostics. In the first case we study new holographic dark energy model without viscous and obtain power-law expansion of the universe which gives constant deceleration parameter and statefinder parameters. In the limit of the parameter, the model approaches to Λ CDM model. In new holographic dark energy model with viscous, the bulk viscous coefficient is assumed as ζ =ζ 0+ζ 1H, where ζ 0 and ζ 1 are constants, and H is the Hubble parameter. In this model, we obtain all possible solutions with viscous term and analyze the expansion history of the universe. We draw the evolution graphs of the scale factor and deceleration parameter. It is observed that the universe transits from deceleration to acceleration for small values of ζ in late time. However, it accelerates very fast from the beginning for large values of ζ . By illustrating the evolutionary trajectories in r-s and r-q planes, we find that our model behaves as an quintessence like for small values of viscous coefficient and a Chaplygin gas like for large values of bulk viscous coefficient at early stage. However, model has close resemblance to that of the Λ CDM cosmology in late time. The Om has positive and negative curvatures for phantom and quintessence models, respectively depending on ζ . Our study shows that the bulk viscosity plays very important role in the expansion history of the universe.

High-speed data duplication/data distribution: An adjunct to the mass storage equation

NASA Technical Reports Server (NTRS)

Howard, Kevin

1993-01-01

The term 'mass storage' invokes the image of large on-site disk and tape farms which contain huge quantities of low- to medium-access data. Although the cost of such bulk storage is recognized, the cost of the bulk distribution of this data rarely is given much attention. Mass data distribution becomes an even more acute problem if the bulk data is part of a national or international system. If the bulk data distribution is to travel from one large data center to another large data center then fiber-optic cables or the use of satellite channels is feasible. However, if the distribution must be disseminated from a central site to a number of much smaller, and, perhaps varying sites, then cost prohibits the use of fiber-optic cable or satellite communication. Given these cost constraints much of the bulk distribution of data will continue to be disseminated via inexpensive magnetic tape using the various next day postal service options. For non-transmitted bulk data, our working hypotheses are that the desired duplication efficiency of the total bulk data should be established before selecting any particular data duplication system; and, that the data duplication algorithm should be determined before any bulk data duplication method is selected.

The impact of baryonic matter on gravitational lensing by galaxy clusters

NASA Astrophysics Data System (ADS)

Lee, Brandyn E.; King, Lindsay; Applegate, Douglas; McCarthy, Ian

2017-01-01

Since the bulk of the matter comprising galaxy clusters exists in the form of dark matter, gravitational N-body simulations have historically been an effective way to investigate large scale structure formation and the astrophysics of galaxy clusters. However, upcoming telescopes such as the Large Synoptic Survey Telescope are expected to have lower systematic errors than older generations, reducing measurement uncertainties and requiring that astrophysicists better quantify the impact of baryonic matter on the cluster lensing signal. Here we outline the effects of baryonic processes on cluster density profiles and on weak lensing mass and concentration estimates. Our analysis is done using clusters grown in the suite of cosmological hydrodynamical simulations known as cosmo-OWLS.

Immunogenicity and safety of the candidate RTS,S/AS01 vaccine in young Nigerian children: a randomized, double-blind, lot-to-lot consistency trial.

PubMed

Umeh, Rich; Oguche, Stephen; Oguonu, Tagbo; Pitmang, Simon; Shu, Elvis; Onyia, Jude-Tony; Daniyam, Comfort A; Shwe, David; Ahmad, Abdullahi; Jongert, Erik; Catteau, Grégory; Lievens, Marc; Ofori-Anyinam, Opokua; Leach, Amanda

2014-11-12

For regulatory approval, consistency in manufacturing of vaccine lots is expected to be demonstrated in confirmatory immunogenicity studies using two-sided equivalence trials. This randomized, double-blind study (NCT01323972) assessed consistency of three RTS,S/AS01 malaria vaccine batches formulated from commercial-scale purified antigen bulk lots in terms of anti-CS-responses induced. Healthy children aged 5-17 months were randomized (1:1:1:1) to receive RTS,S/AS01 at 0-1-2 months from one of three commercial-scale purified antigen bulk lots (1600 litres-fermentation scale; commercial-scale lots), or a comparator vaccine batch made from pilot-scale purified antigen bulk lot (20 litres-fermentation scale; pilot-scale lot). The co-primary objectives were to first demonstrate consistency of antibody responses against circumsporozoite (CS) protein at one month post-dose 3 for the three commercial-scale lots and second demonstrate non-inferiority of anti-CS antibody responses at one month post-dose 3 for the commercial-scale lots compared to the pilot-scale lot. Safety and reactogenicity were evaluated as secondary endpoints. One month post-dose-3, anti-CS antibody geometric mean titres (GMT) for the 3 commercial scale lots were 319.6 EU/ml (95% confidence interval (CI): 268.9-379.8), 241.4 EU/ml (207.6-280.7), and 302.3 EU/ml (259.4-352.3). Consistency for the RTS,S/AS01 commercial-scale lots was demonstrated as the two-sided 95% CI of the anti-CS antibody GMT ratio between each pair of lots was within the range of 0.5-2.0. GMT of the pooled commercial-scale lots (285.8 EU/ml (260.7-313.3)) was non-inferior to the pilot-scale lot (271.7 EU/ml (228.5-323.1)). Each RTS,S/AS01 lot had an acceptable tolerability profile, with infrequent reports of grade 3 solicited symptoms. No safety signals were identified and no serious adverse events were considered related to vaccination. RTS,S/AS01 lots formulated from commercial-scale purified antigen bulk batches induced a consistent anti-CS antibody response, and the anti-CS GMT of pooled commercial-scale lots was non-inferior to that of a lot formulated from a pilot-scale antigen bulk batch. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Cytoskeletal dynamics in fission yeast: a review of models for polarization and division

PubMed Central

Drake, Tyler; Vavylonis, Dimitrios

2010-01-01

We review modeling studies concerning cytoskeletal activity of fission yeast. Recent models vary in length and time scales, describing a range of phenomena from cellular morphogenesis to polymer assembly. The components of cytoskeleton act in concert to mediate cell-scale events and interactions such as polarization. The mathematical models reduce these events and interactions to their essential ingredients, describing the cytoskeleton by its bulk properties. On a smaller scale, models describe cytoskeletal subcomponents and how bulk properties emerge. PMID:21119765

Atomic-Level Sculpting of Crystalline Oxides: Toward Bulk Nanofabrication with Single Atomic Plane Precision.

PubMed

Jesse, Stephen; He, Qian; Lupini, Andrew R; Leonard, Donovan N; Oxley, Mark P; Ovchinnikov, Oleg; Unocic, Raymond R; Tselev, Alexander; Fuentes-Cabrera, Miguel; Sumpter, Bobby G; Pennycook, Stephen J; Kalinin, Sergei V; Borisevich, Albina Y

2015-11-25

The atomic-level sculpting of 3D crystalline oxide nanostructures from metastable amorphous films in a scanning transmission electron microscope (STEM) is demonstrated. Strontium titanate nanostructures grow epitaxially from the crystalline substrate following the beam path. This method can be used for fabricating crystalline structures as small as 1-2 nm and the process can be observed in situ with atomic resolution. The fabrication of arbitrary shape structures via control of the position and scan speed of the electron beam is further demonstrated. Combined with broad availability of the atomic resolved electron microscopy platforms, these observations suggest the feasibility of large scale implementation of bulk atomic-level fabrication as a new enabling tool of nanoscience and technology, providing a bottom-up, atomic-level complement to 3D printing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Eutectic Nano-Droplet Template Injection into Bulk Silicon to Construct Porous Frameworks with Concomitant Conformal Coating as Anodes for Li-Ion Batteries

PubMed Central

Qu, Fei; Li, Chilin; Wang, Zumin; Wen, Yuren; Richter, Gunther; Strunk, Horst P.

2015-01-01

Building porosity in monolithic materials is highly desired to design 3D electrodes, however ex-situ introduction or in-situ generation of nano-scale sacrificial template is still a great challenge. Here Al-Si eutectic droplet templates are uniformly injected into bulk Si through Al-induced solid-solid convection to construct a highly porous Si framework. This process is concomitant with process-inherent conformal coating of ion-conductive oxide. Such an all-in-one method has generated a (continuously processed) high-capacity Si anode integrating longevity and stable electrolyte-anode diaphragm for Li-ion batteries (e.g. a reversible capacity as large as ~1800 mAh/g or ~350 μAh/cm2-μm with a CE of ~99% at 0.1 C after long-term 400 cycles). PMID:25988370

Ultrasound exfoliation of inorganic analogues of graphene

PubMed Central

2014-01-01

High-intensity ultrasound exfoliation of a bulk-layered material is an attractive route for large-scale preparation of monolayers. The monolayer slices could potentially be prepared with a high yield (up to 100%) in a few minutes. Exfoliation of natural minerals (such as tungstenite and molybdenite) or bulk synthetic materials (including hexagonal boron nitride (h-BN), hexagonal boron carbon nitride (h-BCN), and graphitic carbon nitride (g-C3N4)) in liquids leads to the breakdown of the 3D graphitic structure into a 2D structure; the efficiency of this process is highly dependent upon the physical effects of the ultrasound. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were employed to verify the quality of the exfoliation. Herein, this new method of exfoliation with ultrasound assistance for application to mono- and bilayered materials in hydrophobic and hydrophilic environments is presented. PMID:24708572

Ultrasound exfoliation of inorganic analogues of graphene.

PubMed

Stengl, Václav; Henych, Jiří; Slušná, Michaela; Ecorchard, Petra

2014-04-05

High-intensity ultrasound exfoliation of a bulk-layered material is an attractive route for large-scale preparation of monolayers. The monolayer slices could potentially be prepared with a high yield (up to 100%) in a few minutes. Exfoliation of natural minerals (such as tungstenite and molybdenite) or bulk synthetic materials (including hexagonal boron nitride (h-BN), hexagonal boron carbon nitride (h-BCN), and graphitic carbon nitride (g-C3N4)) in liquids leads to the breakdown of the 3D graphitic structure into a 2D structure; the efficiency of this process is highly dependent upon the physical effects of the ultrasound. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were employed to verify the quality of the exfoliation. Herein, this new method of exfoliation with ultrasound assistance for application to mono- and bilayered materials in hydrophobic and hydrophilic environments is presented.

Eutectic nano-droplet template injection into bulk silicon to construct porous frameworks with concomitant conformal coating as anodes for Li-ion batteries.

PubMed

Qu, Fei; Li, Chilin; Wang, Zumin; Wen, Yuren; Richter, Gunther; Strunk, Horst P

2015-05-19

Building porosity in monolithic materials is highly desired to design 3D electrodes, however ex-situ introduction or in-situ generation of nano-scale sacrificial template is still a great challenge. Here Al-Si eutectic droplet templates are uniformly injected into bulk Si through Al-induced solid-solid convection to construct a highly porous Si framework. This process is concomitant with process-inherent conformal coating of ion-conductive oxide. Such an all-in-one method has generated a (continuously processed) high-capacity Si anode integrating longevity and stable electrolyte-anode diaphragm for Li-ion batteries (e.g. a reversible capacity as large as ~1800 mAh/g or ~350 μAh/cm(2)-μm with a CE of ~99% at 0.1 C after long-term 400 cycles).

The Properties of Extragalactic Radio Jets

NASA Astrophysics Data System (ADS)

Finke, Justin

2018-01-01

I show that by assuming a standard Blandford-Konigl jet, it is possible to determine the speed (bulk Lorentz factor) and orientation (angle to the line of sight) of self-similar parsec-scale blazar jets by using four measured quantities: the core radio flux, the extended radio flux, the magnitude of the core shift between two frequencies, and the apparent jet opening angle. Once the bulk Lorentz factor and angle to the line of sight of a jet are known, it is possible to compute their Doppler factor, magnetic field, and intrinsic jet opening angle. I use data taken from the literature and marginalize over nuisance parameters associated with the electron distribution and equipartition, to compute these quantities, albeit with large errors. The results have implications for the resolution of the TeV BL Lac Doppler factor crisis and the production of jets from magnetically arrested disks.

Flexo-photovoltaic effect.

PubMed

Yang, Ming-Min; Kim, Dong Jik; Alexe, Marin

2018-05-25

It is highly desirable to discover photovoltaic mechanisms that enable enhanced efficiency of solar cells. Here we report that the bulk photovoltaic effect, which is free from the thermodynamic Shockley-Queisser limit but usually manifested only in noncentrosymmetric (piezoelectric or ferroelectric) materials, can be realized in any semiconductor, including silicon, by mediation of flexoelectric effect. We used either an atomic force microscope or a micrometer-scale indentation system to introduce strain gradients, thus creating very large photovoltaic currents from centrosymmetric single crystals of strontium titanate, titanium dioxide, and silicon. This strain gradient-induced bulk photovoltaic effect, which we call the flexo-photovoltaic effect, functions in the absence of a p-n junction. This finding may extend present solar cell technologies by boosting the solar energy conversion efficiency from a wide pool of established semiconductors. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Magnetic small-angle neutron scattering on bulk metallic glasses: A feasibility study for imaging displacement fields

NASA Astrophysics Data System (ADS)

Mettus, Denis; Deckarm, Michael; Leibner, Andreas; Birringer, Rainer; Stolpe, Moritz; Busch, Ralf; Honecker, Dirk; Kohlbrecher, Joachim; Hautle, Patrick; Niketic, Nemanja; Fernández, Jesús Rodríguez; Barquín, Luis Fernández; Michels, Andreas

2017-12-01

Magnetic-field-dependent small-angle neutron scattering (SANS) has been utilized to study the magnetic microstructure of bulk metallic glasses (BMGs). In particular, the magnetic scattering from soft magnetic Fe70Mo5Ni5P12.5B2.5C5 and hard magnetic (Nd60Fe30Al10) 92Ni8 alloys in the as-prepared, aged, and mechanically deformed state is compared. While the soft magnetic BMGs exhibit a large field-dependent SANS response with perturbations originating predominantly from spatially varying magnetic anisotropy fields, the SANS cross sections of the hard magnetic BMGs are only weakly dependent on the field, and their angular anisotropy indicates the presence of scattering contributions due to spatially dependent saturation magnetization. Moreover, we observe an unusual increase in the magnetization of the rare-earth-based alloy after deformation. Analysis of the SANS cross sections in terms of the correlation function of the spin misalignment reveals the existence of field-dependent anisotropic long-wavelength magnetization fluctuations on a scale of a few tens of nanometers. We also give a detailed account of how the SANS technique relates to unraveling displacement fields on a mesoscopic length scale in disordered magnetic materials.

Efficient mixing of the solar nebula from uniform Mo isotopic composition of meteorites.

PubMed

Becker, Harry; Walker, Richard J

2003-09-11

The abundances of elements and their isotopes in our Galaxy show wide variations, reflecting different nucleosynthetic processes in stars and the effects of Galactic evolution. These variations contrast with the uniformity of stable isotope abundances for many elements in the Solar System, which implies that processes efficiently homogenized dust and gas from different stellar sources within the young solar nebula. However, isotopic heterogeneity has been recognized on the subcentimetre scale in primitive meteorites, indicating that these preserve a compositional memory of their stellar sources. Small differences in the abundance of stable molybdenum isotopes in bulk rocks of some primitive and differentiated meteorites, relative to terrestrial Mo, suggest large-scale Mo isotopic heterogeneity between some inner Solar System bodies, which implies physical conditions that did not permit efficient mixing of gas and dust. Here we report Mo isotopic data for bulk samples of primitive and differentiated meteorites that show no resolvable deviations from terrestrial Mo. This suggests efficient mixing of gas and dust in the solar nebula at least to 3 au from the Sun, possibly induced by magnetohydrodynamic instabilities. These mixing processes must have occurred before isotopic fractionation of gas-phase elements and volatility-controlled chemical fractionations were established.

Volumes and bulk densities of forty asteroids from ADAM shape modeling

NASA Astrophysics Data System (ADS)

Hanuš, J.; Viikinkoski, M.; Marchis, F.; Ďurech, J.; Kaasalainen, M.; Delbo', M.; Herald, D.; Frappa, E.; Hayamizu, T.; Kerr, S.; Preston, S.; Timerson, B.; Dunham, D.; Talbot, J.

2017-05-01

Context. Disk-integrated photometric data of asteroids do not contain accurate information on shape details or size scale. Additional data such as disk-resolved images or stellar occultation measurements further constrain asteroid shapes and allow size estimates. Aims: We aim to use all the available disk-resolved images of approximately forty asteroids obtained by the Near-InfraRed Camera (Nirc2) mounted on the W.M. Keck II telescope together with the disk-integrated photometry and stellar occultation measurements to determine their volumes. We can then use the volume, in combination with the known mass, to derive the bulk density. Methods: We downloaded and processed all the asteroid disk-resolved images obtained by the Nirc2 that are available in the Keck Observatory Archive (KOA). We combined optical disk-integrated data and stellar occultation profiles with the disk-resolved images and use the All-Data Asteroid Modeling (ADAM) algorithm for the shape and size modeling. Our approach provides constraints on the expected uncertainty in the volume and size as well. Results: We present shape models and volume for 41 asteroids. For 35 of these asteroids, the knowledge of their mass estimates from the literature allowed us to derive their bulk densities. We see a clear trend of lower bulk densities for primitive objects (C-complex) and higher bulk densities for S-complex asteroids. The range of densities in the X-complex is large, suggesting various compositions. We also identified a few objects with rather peculiar bulk densities, which is likely a hint of their poor mass estimates. Asteroid masses determined from the Gaia astrometric observations should further refine most of the density estimates.

Bulk viscous corrections to screening and damping in QCD at high temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Qianqian; Dumitru, Adrian; Guo, Yun

2017-01-01

Non-equilibrium corrections to the distribution functions of quarks and gluons in a hot and dense QCD medium modify the \\hard thermal loops" (HTL). The HTLs determine the retarded, advanced, and symmetric (time-ordered) propagators for gluons with soft momenta as well as the Debye screening and Landau damping mass scales. Here, we compute such corrections to a thermal as well as to a non-thermal fixed point. The screening and damping mass scales are sensitive to the bulk pressure and hence to (pseudo-) critical dynamical scaling of the bulk viscosity in the vicinity of a second-order critical point. This could be reectedmore » in the properties of quarkonium bound states in the deconfined phase and in the dynamics of soft gluon fields.« less

Atomistic Simulation of Initiation in Hexanitrostilbene

NASA Astrophysics Data System (ADS)

Shan, Tzu-Ray; Wixom, Ryan; Yarrington, Cole; Thompson, Aidan

2015-06-01

We report on the effect of cylindrical voids on hot spot formation, growth and chemical reaction initiation in hexanitrostilbene (HNS) crystals subjected to shock. Large-scale, reactive molecular dynamics simulations are performed using the reactive force field (ReaxFF) as implemented in the LAMMPS software. The ReaxFF force field description for HNS has been validated previously by comparing the isothermal equation of state to available diamond anvil cell (DAC) measurements and density function theory (DFT) calculations and by comparing the primary dissociation pathway to ab initio calculations. Micron-scale molecular dynamics simulations of a supported shockwave propagating through the HNS crystal along the [010] orientation are performed with an impact velocity (or particle velocity) of 1.25 km/s, resulting in shockwave propagation at 4.0 km/s in the bulk material and a bulk shock pressure of ~ 11GPa. The effect of cylindrical void sizes varying from 0.02 to 0.1 μm on hot spot formation and growth rate has been studied. Interaction between multiple voids in the HNS crystal and its effect on hot spot formation will also be addressed. Results from the micron-scale atomistic simulations are compared with hydrodynamics simulations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Complex Behavior of Aqueous α-Cyclodextrin Solutions. Interfacial Morphologies Resulting from Bulk Aggregation.

PubMed

Hernandez-Pascacio, Jorge; Piñeiro, Ángel; Ruso, Juan M; Hassan, Natalia; Campbell, Richard A; Campos-Terán, José; Costas, Miguel

2016-07-05

The spontaneous aggregation of α-cyclodextrin (α-CD) molecules in the bulk aqueous solution and the interactions of the resulting aggregates at the liquid/air interface have been studied at 283 K using a battery of techniques: transmission electron microscopy, dynamic light scattering, dynamic surface tensiometry, Brewster angle microscopy, neutron reflectometry, and ellipsometry. We show that α-CD molecules spontaneously form aggregates in the bulk that grow in size with time. These aggregates adsorb to the liquid/air interface with their size in the bulk determining the adsorption rate. The material that reaches the interface coalesces laterally to form two-dimensional domains on the micrometer scale with a layer thickness on the nanometer scale. These processes are affected by the ages of both the bulk and the interface. The interfacial layer formed is not in fast dynamic equilibrium with the subphase as the resulting morphology is locked in a kinetically trapped state. These results reveal a surprising complexity of the parallel physical processes taking place in the bulk and at the interface of what might have seemed initially like a simple system.

Electrodeposition of hierarchically structured three-dimensional nickel–iron electrodes for efficient oxygen evolution at high current densities

PubMed Central

Lu, Xunyu; Zhao, Chuan

2015-01-01

Large-scale industrial application of electrolytic splitting of water has called for the development of oxygen evolution electrodes that are inexpensive, robust and can deliver large current density (>500 mA cm−2) at low applied potentials. Here we show that an efficient oxygen electrode can be developed by electrodepositing amorphous mesoporous nickel–iron composite nanosheets directly onto macroporous nickel foam substrates. The as-prepared oxygen electrode exhibits high catalytic activity towards water oxidation in alkaline solutions, which only requires an overpotential of 200 mV to initiate the reaction, and is capable of delivering current densities of 500 and 1,000 mA cm−2 at overpotentials of 240 and 270 mV, respectively. The electrode also shows prolonged stability against bulk water electrolysis at large current. Collectively, the as-prepared three-dimensional structured electrode is the most efficient oxygen evolution electrode in alkaline electrolytes reported to the best of our knowledge, and can potentially be applied for industrial scale water electrolysis. PMID:25776015

Vortex lattices and defect-mediated viscosity reduction in active liquids

NASA Astrophysics Data System (ADS)

Slomka, Jonasz; Dunkel, Jorn

2016-11-01

Generic pattern-formation and viscosity-reduction mechanisms in active fluids are investigated using a generalized Navier-Stokes model that captures the experimentally observed bulk vortex dynamics in microbial suspensions. We present exact analytical solutions including stress-free vortex lattices and introduce a computational framework that allows the efficient treatment of previously intractable higher-order shear boundary conditions. Large-scale parameter scans identify the conditions for spontaneous flow symmetry breaking, defect-mediated low-viscosity phases and negative-viscosity states amenable to energy harvesting in confined suspensions. The theory uses only generic assumptions about the symmetries and long-wavelength structure of active stress tensors, suggesting that inviscid phases may be achievable in a broad class of non-equilibrium fluids by tuning confinement geometry and pattern scale selection.

Geometry-dependent viscosity reduction in sheared active fluids

NASA Astrophysics Data System (ADS)

Słomka, Jonasz; Dunkel, Jörn

2017-04-01

We investigate flow pattern formation and viscosity reduction mechanisms in active fluids by studying a generalized Navier-Stokes model that captures the experimentally observed bulk vortex dynamics in microbial suspensions. We present exact analytical solutions including stress-free vortex lattices and introduce a computational framework that allows the efficient treatment of higher-order shear boundary conditions. Large-scale parameter scans identify the conditions for spontaneous flow symmetry breaking, geometry-dependent viscosity reduction, and negative-viscosity states amenable to energy harvesting in confined suspensions. The theory uses only generic assumptions about the symmetries and long-wavelength structure of active stress tensors, suggesting that inviscid phases may be achievable in a broad class of nonequilibrium fluids by tuning confinement geometry and pattern scale selection.

The Astrobiological Case for Our Cosmic Ancestry

NASA Astrophysics Data System (ADS)

Wickramasinghe, Chandra

With steadily mounting evidence that points to a cosmic origin of terrestrial life, a cultural barrier prevails against admitting that such a connection exists. Astronomy continues to reveal the presence of organic molecules and organic dust on a huge cosmic scale, amounting to a third of interstellar carbon tied up in this form. Just as the overwhelming bulk of organics on Earth stored over geological timescales are derived from the degradation of living cells, so it seems most likely that interstellar organics in large measure also derive from biology. As we enter a new decade -- the year 2010 -- a clear pronouncement of our likely alien ancestry and of the existence of extraterrestrial life on a cosmic scale would seem to be overdue.

''Tilting'' the universe with the landscape multiverse: the dark flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mersini-Houghton, L.; Holman, R., E-mail: mersini@physics.unc.edu, E-mail: rh4a@andrew.cmu.edu

2009-02-15

We argue that the recent observations of large scale bulk flows by Kashlinsky et al. has a natural explanation in terms of superhorizon inhomogeneities induced by nonlocal entanglement of our Hubble volume with modes and domains beyond the horizon. This entanglement gives rise to corrections to the Newtonian potential on a characteristic scale L{sub 1} {approx_equal} 10{sup 3}H{sup -1}, and it induces a dipole and quadrupole contribution in the CMB. We also show that these induced multipoles are aligned with each other, with the alignment axis normal to their plane being oriented along the preferred frame determined by the dipole.more » We also give other potential tests of our hypothesis.« less

The astrobiological case for our cosmic ancestry

NASA Astrophysics Data System (ADS)

Wickramasinghe, Chandra

2010-04-01

With steadily mounting evidence that points to a cosmic origin of terrestrial life, a cultural barrier prevails against admitting that such a connection exists. Astronomy continues to reveal the presence of organic molecules and organic dust on a huge cosmic scale, amounting to a third of interstellar carbon tied up in this form. Just as the overwhelming bulk of organics on Earth stored over geological timescales are derived from the degradation of living cells, so it seems likely that interstellar organics in large measure also derive from biology. As we enter a new decade - the year 2010 - a clear pronouncement of our likely alien ancestry and of the existence of extraterrestrial life on a cosmic scale would seem to be overdue.

Toxoplasma gondii Antibodies in Bulk Tank Milk Samples of Caprine Dairy Herds.

PubMed

Gazzonis, Alessia Libera; Zanzani, Sergio Aurelio; Stradiotto, Katia; Olivieri, Emanuela; Villa, Luca; Manfredi, Maria Teresa

2018-06-15

A major public health issue, Toxoplasma gondii infection can affect humans mainly via the consumption of animal products from certain species, including small ruminants. Therefore, a regular monitoring of the infection in ovine and caprine populations is advisable for the control of human and animal toxoplasmosis. Antibody detection in individual and bulk tank milk may represent a valid alternative to serological analysis, being its collection easy and not affecting animal welfare. Many serological tools for milk analysis have already been validated for several parasites, including Apicomplexa. Thus, the aim of the present study was to obtain epidemiological data on T. gondii infection through the detection of antibodies in bulk tank milk of dairy goat herds from an important area for caprine dairy production (Northern Italy). The performance of a commercial ELISA was first evaluated for analysis on caprine milk samples, using a panel of serum-milk pairs of goats naturally infected by T. gondii. The analysis on bulk tank milk confirmed the presence of antibodies anti-T. gondii in 59% of the samples. Toxoplasma gondii antibody positivity was more frequently found in farms reared under extensive (64.9%) or semi-intensive systems (68.7%) in comparison to intensive farms (51.1%). Analysis on milk revealed to be a valid alternative to serological tests, being easily applied in large-scale epidemiological surveys and for continuous monitoring of T. gondii infection.

The Power Spectrum of the Milky Way: Velocity Fluctuations in the Galactic Disk

NASA Astrophysics Data System (ADS)

Bovy, Jo; Bird, Jonathan C.; García Pérez, Ana E.; Majewski, Steven R.; Nidever, David L.; Zasowski, Gail

2015-02-01

We investigate the kinematics of stars in the mid-plane of the Milky Way (MW) on scales between 25 pc and 10 kpc with data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the Radial Velocity Experiment (RAVE), and the Geneva-Copenhagen survey (GCS). Using red-clump (RC) stars in APOGEE, we determine the large-scale line-of-sight velocity field out to 5 kpc from the Sun in (0.75 kpc)2 bins. The solar motion V ⊙ - c with respect to the circular velocity Vc is the largest contribution to the power on large scales after subtracting an axisymmetric rotation field; we determine the solar motion by minimizing the large-scale power to be V ⊙ - c = 24 ± 1 (ran.) ± 2 (syst. [Vc ]) ± 5 (syst.[large-scale]) km s-1, where the systematic uncertainty is due to (1) a conservative 20 km s-1 uncertainty in Vc and (2) the estimated power on unobserved larger scales. Combining the APOGEE peculiar-velocity field with RC stars in RAVE out to 2 kpc from the Sun and with local GCS stars, we determine the power spectrum of residual velocity fluctuations in the MW's disk on scales between 0.2 kpc-1 <= k <= 40 kpc-1. Most of the power is contained in a broad peak between 0.2 kpc-1 < k < 0.9 kpc-1. We investigate the expected power spectrum for various non-axisymmetric perturbations and demonstrate that the central bar with commonly used parameters but of relatively high mass can explain the bulk of velocity fluctuations in the plane of the Galactic disk near the Sun. Streaming motions ≈10 km s-1 on >~ 3 kpc scales in the MW are in good agreement with observations of external galaxies and directly explain why local determinations of the solar motion are inconsistent with global measurements.

Time-resolved orbital angular momentum spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noyan, Mehmet A.; Kikkawa, James M.

We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.

Radar and microphysical characteristics of convective storms simulated from a numerical model using a new microphysical parameterization

NASA Technical Reports Server (NTRS)

Ferrier, Brad S.; Tao, Wei-Kuo; Simpson, Joanne

1991-01-01

The basic features of a new and improved bulk-microphysical parameterization capable of simulating the hydrometeor structure of convective systems in all types of large-scale environments (with minimal adjustment of coefficients) are studied. Reflectivities simulated from the model are compared with radar observations of an intense midlatitude convective system. Simulated reflectivities using the novel four-class ice scheme with a microphysical parameterization rain distribution at 105 min are illustrated. Preliminary results indicate that this new ice scheme works efficiently in simulating midlatitude continental storms.

Complex Nano-Scale Structures for Unprecedented Properties in Steels

DOE PAGES

Caballero, Francisca G.; Poplawsky, Jonathan D.; Yen, Hung Wei; ...

2016-11-01

Processing bulk nanoscrystalline materials for structural applications still poses a rather large challenge, particularly in achieving an industrially viable process. In this context, recent work has proved that complex nanoscale steel structures can be formed by solid reaction at low temperatures. These nanocrystalline bainitic steels present the highest strength ever recorded, unprecedented ductility, fatigue on par with commercial bearing steels and exceptional rolling-sliding wear performances. In this paper, a description of the characteristics and significance of these remarkable structures in the context of the atomic mechanism of transformation is provided.

Sodium Flux Growth of Bulk Gallium Nitride

NASA Astrophysics Data System (ADS)

Von Dollen, Paul Martin

This dissertation focused on development of a novel apparatus and techniques for crystal growth of bulk gallium nitride (GaN) using the sodium flux method. Though several methods exist to produce bulk GaN, none have been commercialized on an industrial scale. The sodium flux method offers potentially lower cost production due to relatively mild process conditions while maintaining high crystal quality. But the current equipment and methods for sodium flux growth of bulk GaN are generally not amenable to large-scale crystal growth or in situ investigation of growth processes, which has hampered progress. A key task was to prevent sodium loss or migration from the sodium-gallium growth melt while permitting N2 gas to access the growing crystal, which was accomplished by implementing a reflux condensing stem along with a reusable sealed capsule. The reflux condensing stem also enabled direct monitoring and control of the melt temperature, which has not been previously reported for the sodium flux method. Molybdenum-based materials were identified from a corrosion study as candidates for direct containment of the corrosive sodium-gallium melt. Successful introduction of these materials allowed implementation of a crucible-free containment system, which improved process control and can potentially reduce crystal impurity levels. Using the new growth system, the (0001) Ga face (+c plane) growth rate was >50 mum/hr, which is the highest bulk GaN growth rate reported for the sodium flux method. Omega X-ray rocking curve (?-XRC) measurements indicated the presence of multiple grains, though full width at half maximum (FWHM) values for individual peaks were <100 arcseconds. Oxygen impurity concentrations as measured by secondary ion mass spectroscopy (SIMS) were >1020 atoms/cm3, possibly due to reactor cleaning and handling procedures. This dissertation also introduced an in situ technique to correlate changes in N2 pressure with dissolution of nitrogen and precipitation of GaN from the sodium-gallium melt. Different stages of N2 pressure decay were identified and linked to distinct modes of GaN crystal growth. Based on this analysis, the highest growth rate may have up to 90 mum/hr, and did not appear to be mass-transport limited, in contrast to previous reports. Several refinements and improvements of the novel equipment and methods introduced were also explored, all of which have potential to further advance state of the art sodium flux growth of bulk GaN.

Effects of Mass Fluctuation on Thermal Transport Properties in Bulk Bi2Te3

NASA Astrophysics Data System (ADS)

Huang, Ben; Zhai, Pengcheng; Yang, Xuqiu; Li, Guodong

2017-05-01

In this paper, we applied large-scale molecular dynamics and lattice dynamics to study the influence of mass fluctuation on thermal transport properties in bulk Bi2Te3, namely thermal conductivity ( K), phonon density of state (PDOS), group velocity ( v g), and mean free path ( l). The results show that total atomic mass change can affect the relevant vibrational frequency on the micro level and heat transfer rate in the macro statistic, hence leading to the strength variation of the anharmonic phonon processes (Umklapp scattering) in the defect-free Bi2Te3 bulk. Moreover, it is interesting to find that the anharmonicity of Bi2Te3 can be also influenced by atomic differences of the structure such as the mass distribution in the primitive cell. Considering the asymmetry of the crystal structure and interatomic forces, it can be concluded by phonon frequency, lifetime, and velocity calculation that acoustic-optical phonon scattering shows the structure-sensitivity to the mass distribution and complicates the heat transfer mechanism, hence resulting in the low lattice thermal conductivity of Bi2Te3. This study is helpful for designing the material with tailored thermal conductivity via atomic substitution.

The B → πK puzzle and the bulk Randall-Sundrum model

NASA Astrophysics Data System (ADS)

Chang, Sanghyeon; Kim, C. S.; Song, Jeonghyeon

2011-02-01

The recent measurements of the direct CP asymmetries (ACP) in the penguin-dominated B → Kπ decays show some discrepancy from the standard model (SM) prediction. While ACP of B+ →π0K+ and that of B0 →π-K+ in the naive estimate of the SM are expected to have very similar values, their experimental data are of the opposite sign and different magnitudes. We study the effects of the custodial bulk Randall-Sundrum model on this ACP. In this model, the misalignment of the five-dimensional (5D) Yukawa interactions to the 5D bulk gauge interactions in flavor space leads to tree-level flavor-changing neutral current by the Kaluza-Klein gauge bosons. In a large portion of the parameter space of this model, the observed non-zero ACP (B+ →π0K+) -ACP (B0 →π-K+) can be explained only with low Kaluza-Klein mass scale MKK around 1 TeV. Rather extreme parameters is required to explain it with MKK ≃ 3 TeV. The new contributions to well-measured branching ratios of B → Kπ decays are also shown to be suppressed.

A Deeper Understanding of Stability in the Solar Wind: Applying Nyquist's Instability Criterion to Wind Faraday Cup Data

NASA Astrophysics Data System (ADS)

Alterman, B. L.; Klein, K. G.; Verscharen, D.; Stevens, M. L.; Kasper, J. C.

2017-12-01

Long duration, in situ data sets enable large-scale statistical analysis of free-energy-driven instabilities in the solar wind. The plasma beta and temperature anisotropy plane provides a well-defined parameter space in which a single-fluid plasma's stability can be represented. Because this reduced parameter space can only represent instability thresholds due to the free energy of one ion species - typically the bulk protons - the true impact of instabilities on the solar wind is under estimated. Nyquist's instability criterion allows us to systematically account for other sources of free energy including beams, drifts, and additional temperature anisotropies. Utilizing over 20 years of Wind Faraday cup and magnetic field observations, we have resolved the bulk parameters for three ion populations: the bulk protons, beam protons, and alpha particles. Applying Nyquist's criterion, we calculate the number of linearly growing modes supported by each spectrum and provide a more nuanced consideration of solar wind stability. Using collisional age measurements, we predict the stability of the solar wind close to the sun. Accounting for the free-energy from the three most common ion populations in the solar wind, our approach provides a more complete characterization of solar wind stability.

Feasibility of a multi-component additive for efficient control of activated sludge filamentous bulking.

PubMed

Seka, A M; Van De Wiele, T; Verstraete, W

2001-08-01

Instantaneous improvement of the settling of bulking filamentous activated sludge can be achieved by the addition of a polymer or a large amount (up to 100% of the MLSS concentration) of talc powder to the sludge. Long-term improvement relies on repeated additions, as these additives have no adverse effects on the causative filaments. A multi-component additive was compared to the traditional additives in lab-scale activated sludge units using three highly filamentous sludges from different industrial treatment plants. The study demonstrated that the multi-component additive was superior to the traditional remedies. It was shown that, in the case of severe filamentous bulking, a single addition of the new additive immediately improved sludge settling and exerted a destructive effect on the causative filamentous bacteria. Thus, the latter additive also ensured a long-term sludge sedimentation improvement. The traditional additives exhibited an immediate and short-term effect. The novel additive also retarded sludge rising due to denitrification and it improved sludge dewaterability. The study revealed Nostocoido limicola II, with slightly hydrophobic cell wall, to be somewhat resistant to the quaternary ammonium salt present as biocide in the additive.

Dynamics of the Fouling Layer Microbial Community in a Membrane Bioreactor

PubMed Central

Ziegler, Anja S.; McIlroy, Simon J.; Larsen, Poul; Albertsen, Mads; Hansen, Aviaja A.; Heinen, Nicolas; Nielsen, Per Halkjær

2016-01-01

Membrane fouling presents the greatest challenge to the application of membrane bioreactor (MBR) technology. Formation of biofilms on the membrane surface is the suggested cause, yet little is known of the composition or dynamics of the microbial community responsible. To gain an insight into this important question, we applied 16S rRNA gene amplicon sequencing with a curated taxonomy and fluorescent in situ hybridization to monitor the community of a pilot-scale MBR carrying out enhanced biological nitrogen and phosphorus removal with municipal wastewater. In order to track the dynamics of the fouling process, we concurrently investigated the communities of the biofilm, MBR bulk sludge, and the conventional activated sludge system used to seed the MBR system over several weeks from start-up. As the biofilm matured the initially abundant betaproteobacterial genera Limnohabitans, Hydrogenophaga and Malikia were succeeded by filamentous Chloroflexi and Gordonia as the abundant species. This study indicates that, although putative pioneer species appear, the biofilm became increasingly similar to the bulk community with time. This suggests that the microbial population in bulk water will largely determine the community structure of the mature biofilm. PMID:27399199

Void asymmetries in the cosmic web: a mechanism for bulk flows

NASA Astrophysics Data System (ADS)

Bland-Hawthorn, J.; Sharma, S.

2016-10-01

Bulk flows of galaxies moving with respect to the cosmic microwave background are well established observationally and seen in the most recent ΛCDM simulations. With the aid of an idealised Gadget-2 simulation, we show that void asymmetries in the cosmic web can exacerbate local bulk flows of galaxies. The {\\it Cosmicflows-2} survey, which has mapped in detail the 3D structure of the Local Universe, reveals that the Local Group resides in a ``local sheet'' of galaxies that borders a ``local void'' with a diameter of about 40 Mpc. The void is emptying out at a rate of 16 km s-1 Mpc-1. In a co-moving frame, the Local Sheet is found to be moving away from the Local Void at ~ 260 km s-1. Our model shows how asymmetric collapse due to unbalanced voids on either side of a developing sheet or wall can lead to a systematic movement of the sheet. We conjectured that asymmetries could lead to a large-scale separation of dark matter and baryons, thereby driving a dependence of galaxy properties with environment, but we do {\\it not} find any evidence for this effect.

Efficient bulk-loading of gridfiles

NASA Technical Reports Server (NTRS)

Leutenegger, Scott T.; Nicol, David M.

1994-01-01

This paper considers the problem of bulk-loading large data sets for the gridfile multiattribute indexing technique. We propose a rectilinear partitioning algorithm that heuristically seeks to minimize the size of the gridfile needed to ensure no bucket overflows. Empirical studies on both synthetic data sets and on data sets drawn from computational fluid dynamics applications demonstrate that our algorithm is very efficient, and is able to handle large data sets. In addition, we present an algorithm for bulk-loading data sets too large to fit in main memory. Utilizing a sort of the entire data set it creates a gridfile without incurring any overflows.

Quantum oscillations in a topological insulator Bi2Te2Se with large bulk resistivity (6 Ω cm)

NASA Astrophysics Data System (ADS)

Xiong, Jun; Petersen, A. C.; Qu, Dongxia; Hor, Y. S.; Cava, R. J.; Ong, N. P.

2012-02-01

We report the observation of prominent Shubnikov-de Haas oscillations in a Topological Insulator, Bi2Te2Se, with large bulk resistivity (6 Ω cm at 4 K). By fitting the SdH oscillations, we infer a large metallicity parameter kFℓ=41, with a surface mobility (μs∼2800 cm2/V s) much larger than the bulk mobility (μb∼50 cm2/V s). The plot of the index fields Bν vs. filling factor ν shows a {1}/{2}-shift, consistent with massless, Dirac states.

Role of Spatial Ionic Distribution on the Energetics of Hydrophobic Assembly and Properties of the Water/Hydrophobe Interface†

PubMed Central

Bauer, Brad A.; Ou, Shuching; Patel, Sandeep

2014-01-01

We present results from all-atom molecular dynamics simulations of large-scale hydrophobic plates solvated in NaCl and NaI salt solutions. As observed in studies of ions at the air-water interface, the density of iodide near the water-plate interface is significantly enhanced relative to chloride and in the bulk. This allows for the partial hydration of iodide while chloride remains more fully hydrated. In 1M solutions, iodide directly pushes the hydrophobes together (contributing −2.51 kcal/mol) to the PMF. Chloride, however, strengthens the water-induced contribution to the PMF by ~ −2.84 kcal/mol. These observations are enhanced in 3M solutions, consistent with the increased ion density in the vicinity of the hydrophobes. The different salt solutions influence changes in the critical hydrophobe separation distance and characteristic wetting/dewetting transitions. These differences are largely influenced by the ion-specific expulsion of iodide from bulk water. Results of this study are of general interest to the study of ions at interfaces and may lend insight to the mechanisms underlying the Hofmeister series. PMID:22231014

Holographic self-tuning of the cosmological constant

NASA Astrophysics Data System (ADS)

Charmousis, Christos; Kiritsis, Elias; Nitti, Francesco

2017-09-01

We propose a brane-world setup based on gauge/gravity duality in which the four-dimensional cosmological constant is set to zero by a dynamical self-adjustment mechanism. The bulk contains Einstein gravity and a scalar field. We study holographic RG flow solutions, with the standard model brane separating an infinite volume UV region and an IR region of finite volume. For generic values of the brane vacuum energy, regular solutions exist such that the four-dimensional brane is flat. Its position in the bulk is determined dynamically by the junction conditions. Analysis of linear fluctuations shows that a regime of 4-dimensional gravity is possible at large distances, due to the presence of an induced gravity term. The graviton acquires an effective mass, and a five-dimensional regime may exist at large and/or small scales. We show that, for a broad choice of potentials, flat-brane solutions are manifestly stable and free of ghosts. We compute the scalar contribution to the force between brane-localized sources and show that, in certain models, the vDVZ discontinuity is absent and the effective interaction at short distances is mediated by two transverse graviton helicities.

Controlling the scattering properties of thin, particle-doped coatings

NASA Astrophysics Data System (ADS)

Rogers, William; Corbett, Madeleine; Manoharan, Vinothan

2013-03-01

Coatings and thin films of small particles suspended in a matrix possess optical properties that are important in several industries from cosmetics and paints to polymer composites. Many of the most interesting applications require coatings that produce several bulk effects simultaneously, but it is often difficult to rationally formulate materials with these desired optical properties. Here, we focus on the specific challenge of designing a thin colloidal film that maximizes both diffuse and total hemispherical transmission. We demonstrate that these bulk optical properties follow a simple scaling with two microscopic length scales: the scattering and transport mean free paths. Using these length scales and Mie scattering calculations, we generate basic design rules that relate scattering at the single particle level to the film's bulk optical properties. These ideas will be useful in the rational design of future optically active coatings.

Random deposition of particles of different sizes.

PubMed

Forgerini, F L; Figueiredo, W

2009-04-01

We study the surface growth generated by the random deposition of particles of different sizes. A model is proposed where the particles are aggregated on an initially flat surface, giving rise to a rough interface and a porous bulk. By using Monte Carlo simulations, a surface has grown by adding particles of different sizes, as well as identical particles on the substrate in (1+1) dimensions. In the case of deposition of particles of different sizes, they are selected from a Poisson distribution, where the particle sizes may vary by 1 order of magnitude. For the deposition of identical particles, only particles which are larger than one lattice parameter of the substrate are considered. We calculate the usual scaling exponents: the roughness, growth, and dynamic exponents alpha, beta, and z, respectively, as well as, the porosity in the bulk, determining the porosity as a function of the particle size. The results of our simulations show that the roughness evolves in time following three different behaviors. The roughness in the initial times behaves as in the random deposition model. At intermediate times, the surface roughness grows slowly and finally, at long times, it enters into the saturation regime. The bulk formed by depositing large particles reveals a porosity that increases very fast at the initial times and also reaches a saturation value. Excepting the case where particles have the size of one lattice spacing, we always find that the surface roughness and porosity reach limiting values at long times. Surprisingly, we find that the scaling exponents are the same as those predicted by the Villain-Lai-Das Sarma equation.

Brane-World Gravity.

PubMed

Maartens, Roy; Koyama, Kazuya

2010-01-01

The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+ d -dimensional spacetime (the "bulk"), with Standard Model particles and fields trapped on the brane while gravity is free to access the bulk. At least one of the d extra spatial dimensions could be very large relative to the Planck scale, which lowers the fundamental gravity scale, possibly even down to the electroweak (∼ TeV) level. This revolutionary picture arises in the framework of recent developments in M theory. The 1+10-dimensional M theory encompasses the known 1+9-dimensional superstring theories, and is widely considered to be a promising potential route to quantum gravity. At low energies, gravity is localized at the brane and general relativity is recovered, but at high energies gravity "leaks" into the bulk, behaving in a truly higher-dimensional way. This introduces significant changes to gravitational dynamics and perturbations, with interesting and potentially testable implications for high-energy astrophysics, black holes, and cosmology. Brane-world models offer a phenomenological way to test some of the novel predictions and corrections to general relativity that are implied by M theory. This review analyzes the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane-worlds based on the Randall-Sundrum models. We also cover the simplest brane-world models in which 4-dimensional gravity on the brane is modified at low energies - the 5-dimensional Dvali-Gabadadze-Porrati models. Then we discuss co-dimension two branes in 6-dimensional models.

Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations

DOE PAGES

Ihlefeld, Jon F.; Harris, David T.; Keech, Ryan; ...

2016-07-05

Ferroelectric materials are well-suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro-optic devices, and non-volatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a non-centrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change of properties withmore » decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, while in bulk ceramics, changes in properties from the values of large-grained specimens is most notable in samples with grain sizes below several microns. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics are reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. Ultimately, in many cases, multiple mechanisms combine to produce the observed scaling effects.« less

Principle of Parsimony, Fake Science, and Scales

NASA Astrophysics Data System (ADS)

Yeh, T. C. J.; Wan, L.; Wang, X. S.

2017-12-01

Considering difficulties in predicting exact motions of water molecules, and the scale of our interests (bulk behaviors of many molecules), Fick's law (diffusion concept) has been created to predict solute diffusion process in space and time. G.I. Taylor (1921) demonstrated that random motion of the molecules reach the Fickian regime in less a second if our sampling scale is large enough to reach ergodic condition. Fick's law is widely accepted for describing molecular diffusion as such. This fits the definition of the parsimony principle at the scale of our concern. Similarly, advection-dispersion or convection-dispersion equation (ADE or CDE) has been found quite satisfactory for analysis of concentration breakthroughs of solute transport in uniformly packed soil columns. This is attributed to the solute is often released over the entire cross-section of the column, which has sampled many pore-scale heterogeneities and met the ergodicity assumption. Further, the uniformly packed column contains a large number of stationary pore-size heterogeneity. The solute thus reaches the Fickian regime after traveling a short distance along the column. Moreover, breakthrough curves are concentrations integrated over the column cross-section (the scale of our interest), and they meet the ergodicity assumption embedded in the ADE and CDE. To the contrary, scales of heterogeneity in most groundwater pollution problems evolve as contaminants travel. They are much larger than the scale of our observations and our interests so that the ergodic and the Fickian conditions are difficult. Upscaling the Fick's law for solution dispersion, and deriving universal rules of the dispersion to the field- or basin-scale pollution migrations are merely misuse of the parsimony principle and lead to a fake science ( i.e., the development of theories for predicting processes that can not be observed.) The appropriate principle of parsimony for these situations dictates mapping of large-scale heterogeneities as detailed as possible and adapting the Fick's law for effects of small-scale heterogeneity resulting from our inability to characterize them in detail.

Sub-second thermoplastic forming of bulk metallic glasses by ultrasonic beating

PubMed Central

Ma, Jiang; Liang, Xiong; Wu, Xiaoyu; Liu, Zhiyuan; Gong, Feng

2015-01-01

The work proposed a novel thermoplastic forming approach–the ultrasonic beating forming (UBF) method for bulk metallic glasses (BMGs) in present work. The rapid forming approach can finish the thermoplastic forming of BMGs in less than one second, avoiding the time-dependent crystallization and oxidation to the most extent. Besides, the UBF is also proved to be competent in the fabrication of structures with the length scale ranging from macro scale to nano scale. Our results propose a novel route for the thermoplastic forming of BMGs and have promising applications in the rapid fabrication of macro to nano scale products and devices. PMID:26644149

Sensing, Measuring and Modelling the Mechanical Properties of Sandstone

NASA Astrophysics Data System (ADS)

Antony, S. J.; Olugbenga, A.; Ozerkan, N. G.

2018-02-01

We present a hybrid framework for simulating the strength and dilation characteristics of sandstone. Where possible, the grain-scale properties of sandstone are evaluated experimentally in detail. Also, using photo-stress analysis, we sense the deviator stress (/strain) distribution at the micro-scale and its components along the orthogonal directions on the surface of a V-notch sandstone sample under mechanical loading. Based on this measurement and applying a grain-scale model, the optical anisotropy index K 0 is inferred at the grain scale. This correlated well with the grain contact stiffness ratio K evaluated using ultrasound sensors independently. Thereafter, in addition to other experimentally characterised structural and grain-scale properties of sandstone, K is fed as an input into the discrete element modelling of fracture strength and dilation of the sandstone samples. Physical bulk-scale experiments are also conducted to evaluate the load-displacement relation, dilation and bulk fracture strength characteristics of sandstone samples under compression and shear. A good level of agreement is obtained between the results of the simulations and experiments. The current generic framework could be applied to understand the internal and bulk mechanical properties of such complex opaque and heterogeneous materials more realistically in future.

Large-scale single-chirality separation of single-wall carbon nanotubes by simple gel chromatography

PubMed Central

Liu, Huaping; Nishide, Daisuke; Tanaka, Takeshi; Kataura, Hiromichi

2011-01-01

Monostructured single-wall carbon nanotubes (SWCNTs) are important in both scientific research and electronic and biomedical applications; however, the bulk separation of SWCNTs into populations of single-chirality nanotubes remains challenging. Here we report a simple and effective method for the large-scale chirality separation of SWCNTs using a single-surfactant multicolumn gel chromatography method utilizing one surfactant and a series of vertically connected gel columns. This method is based on the structure-dependent interaction strength of SWCNTs with an allyl dextran-based gel. Overloading an SWCNT dispersion on the top column results in the adsorption sites of the column becoming fully occupied by the nanotubes that exhibit the strongest interaction with the gel. The unbound nanotubes flow through to the next column, and the nanotubes with the second strongest interaction with the gel are adsorbed in this stage. In this manner, 13 different (n, m) species were separated. Metallic SWCNTs were finally collected as unbound nanotubes because they exhibited the lowest interaction with the gel. PMID:21556063

Using adaptive-mesh refinement in SCFT simulations of surfactant adsorption

NASA Astrophysics Data System (ADS)

Sides, Scott; Kumar, Rajeev; Jamroz, Ben; Crockett, Robert; Pletzer, Alex

2013-03-01

Adsorption of surfactants at interfaces is relevant to many applications such as detergents, adhesives, emulsions and ferrofluids. Atomistic simulations of interface adsorption are challenging due to the difficulty of modeling the wide range of length scales in these problems: the thin interface region in equilibrium with a large bulk region that serves as a reservoir for the adsorbed species. Self-consistent field theory (SCFT) has been extremely useful for studying the morphologies of dense block copolymer melts. Field-theoretic simulations such as these are able to access large length and time scales that are difficult or impossible for particle-based simulations such as molecular dynamics. However, even SCFT methods can be difficult to apply to systems in which small spatial regions might require finer resolution than most of the simulation grid (eg. interface adsorption and confinement). We will present results on interface adsorption simulations using PolySwift++, an object-oriented, polymer SCFT simulation code aided by the Tech-X Chompst library that enables via block-structured AMR calculations with PETSc.

A scalable double-barcode sequencing platform for characterization of dynamic protein-protein interactions.

PubMed

Schlecht, Ulrich; Liu, Zhimin; Blundell, Jamie R; St Onge, Robert P; Levy, Sasha F

2017-05-25

Several large-scale efforts have systematically catalogued protein-protein interactions (PPIs) of a cell in a single environment. However, little is known about how the protein interactome changes across environmental perturbations. Current technologies, which assay one PPI at a time, are too low throughput to make it practical to study protein interactome dynamics. Here, we develop a highly parallel protein-protein interaction sequencing (PPiSeq) platform that uses a novel double barcoding system in conjunction with the dihydrofolate reductase protein-fragment complementation assay in Saccharomyces cerevisiae. PPiSeq detects PPIs at a rate that is on par with current assays and, in contrast with current methods, quantitatively scores PPIs with enough accuracy and sensitivity to detect changes across environments. Both PPI scoring and the bulk of strain construction can be performed with cell pools, making the assay scalable and easily reproduced across environments. PPiSeq is therefore a powerful new tool for large-scale investigations of dynamic PPIs.

Loss of locality in gravitational correlators with a large number of insertions

NASA Astrophysics Data System (ADS)

Ghosh, Sudip; Raju, Suvrat

2017-09-01

We review lessons from the AdS/CFT correspondence that indicate that the emergence of locality in quantum gravity is contingent upon considering observables with a small number of insertions. Correlation functions, where the number of insertions scales with a power of the central charge of the CFT, are sensitive to nonlocal effects in the bulk theory, which arise from a combination of the effects of the bulk Gauss law and a breakdown of perturbation theory. To examine whether a similar effect occurs in flat space, we consider the scattering of massless particles in the bosonic string and the superstring in the limit, where the number of external particles, n, becomes very large. We use estimates of the volume of the Weil-Petersson moduli space of punctured Riemann surfaces to argue that string amplitudes grow factorially in this limit. We verify this factorial behavior through an extensive numerical analysis of string amplitudes at large n. Our numerical calculations rely on the observation that, in the large n limit, the string scattering amplitude localizes on the Gross-Mende saddle points, even though individual particle energies are small. This factorial growth implies the breakdown of string perturbation theory for n ˜(M/plE ) d -2 in d dimensions, where E is the typical individual particle energy. We explore the implications of this breakdown for the black hole information paradox. We show that the loss of locality suggested by this breakdown is precisely sufficient to resolve the cloning and strong subadditivity paradoxes.

Variability and Maintenance of Turbulence in the Very Stable Boundary Layer

NASA Astrophysics Data System (ADS)

Mahrt, Larry

2010-04-01

The relationship of turbulence quantities to mean flow quantities, such as the Richardson number, degenerates substantially for strong stability, at least in those studies that do not place restrictions on minimum turbulence or non-stationarity. This study examines the large variability of the turbulence for very stable conditions by analyzing four months of turbulence data from a site with short grass. Brief comparisons are made with three additional sites, one over short grass on flat terrain and two with tall vegetation in complex terrain. For very stable conditions, any dependence of the turbulence quantities on the mean wind speed or bulk Richardson number becomes masked by large scatter, as found in some previous studies. The large variability of the turbulence quantities is due to random variations and other physical influences not represented by the bulk Richardson number. There is no critical Richardson number above which the turbulence vanishes. For very stable conditions, the record-averaged vertical velocity variance and the drag coefficient increase with the strength of the submeso motions (wave motions, solitary waves, horizontal modes and numerous more complex signatures). The submeso motions are on time scales of minutes and not normally considered part of the mean flow. The generation of turbulence by such unpredictable motions appears to preclude universal similarity theory for predicting the surface stress for very stable conditions. Large variation of the stress direction with respect to the wind direction for the very stable regime is also examined. Needed additional work is noted.

Metabolic Engineering toward Sustainable Production of Nylon-6.

PubMed

Turk, Stefan C H J; Kloosterman, Wigard P; Ninaber, Dennis K; Kolen, Karin P A M; Knutova, Julia; Suir, Erwin; Schürmann, Martin; Raemakers-Franken, Petronella C; Müller, Monika; de Wildeman, Stefaan M A; Raamsdonk, Leonie M; van der Pol, Ruud; Wu, Liang; Temudo, Margarida F; van der Hoeven, Rob A M; Akeroyd, Michiel; van der Stoel, Roland E; Noorman, Henk J; Bovenberg, Roel A L; Trefzer, Axel C

2016-01-15

Nylon-6 is a bulk polymer used for many applications. It consists of the non-natural building block 6-aminocaproic acid, the linear form of caprolactam. Via a retro-synthetic approach, two synthetic pathways were identified for the fermentative production of 6-aminocaproic acid. Both pathways require yet unreported novel biocatalytic steps. We demonstrated proof of these bioconversions by in vitro enzyme assays with a set of selected candidate proteins expressed in Escherichia coli. One of the biosynthetic pathways starts with 2-oxoglutarate and contains bioconversions of the ketoacid elongation pathway known from methanogenic archaea. This pathway was selected for implementation in E. coli and yielded 6-aminocaproic acid at levels up to 160 mg/L in lab-scale batch fermentations. The total amount of 6-aminocaproic acid and related intermediates generated by this pathway exceeded 2 g/L in lab-scale fed-batch fermentations, indicating its potential for further optimization toward large-scale sustainable production of nylon-6.

Scalable ion-photon quantum interface based on integrated diffractive mirrors

NASA Astrophysics Data System (ADS)

Ghadimi, Moji; Blūms, Valdis; Norton, Benjamin G.; Fisher, Paul M.; Connell, Steven C.; Amini, Jason M.; Volin, Curtis; Hayden, Harley; Pai, Chien-Shing; Kielpinski, David; Lobino, Mirko; Streed, Erik W.

2017-12-01

Quantum networking links quantum processors through remote entanglement for distributed quantum information processing and secure long-range communication. Trapped ions are a leading quantum information processing platform, having demonstrated universal small-scale processors and roadmaps for large-scale implementation. Overall rates of ion-photon entanglement generation, essential for remote trapped ion entanglement, are limited by coupling efficiency into single mode fibers and scaling to many ions. Here, we show a microfabricated trap with integrated diffractive mirrors that couples 4.1(6)% of the fluorescence from a 174Yb+ ion into a single mode fiber, nearly triple the demonstrated bulk optics efficiency. The integrated optic collects 5.8(8)% of the π transition fluorescence, images the ion with sub-wavelength resolution, and couples 71(5)% of the collected light into the fiber. Our technology is suitable for entangling multiple ions in parallel and overcomes mode quality limitations of existing integrated optical interconnects.

Atomic-scale structure and electronic properties of GaN/GaAs superlattices

NASA Astrophysics Data System (ADS)

Goldman, R. S.; Feenstra, R. M.; Briner, B. G.; O'Steen, M. L.; Hauenstein, R. J.

1996-12-01

We have investigated the atomic-scale structure and electronic properties of GaN/GaAs superlattices produced by nitridation of a molecular beam epitaxially grown GaAs surface. Using cross-sectional scanning tunneling microscopy (STM) and spectroscopy, we show that the nitrided layers are laterally inhomogeneous, consisting of groups of atomic-scale defects and larger clusters. Analysis of x-ray diffraction data in terms of fractional area of clusters (determined by STM), reveals a cluster lattice constant similar to bulk GaN. In addition, tunneling spectroscopy on the defects indicates a conduction band state associated with an acceptor level of NAs in GaAs. Therefore, we identify the clusters and defects as nearly pure GaN and NAs, respectively. Together, the results reveal phase segregation in these arsenide/nitride structures, in agreement with the large miscibility gap predicted for GaAsN.

RACORO continental boundary layer cloud investigations. Part I: Case study development and ensemble large-scale forcings

DOE PAGES

Vogelmann, Andrew M.; Fridlind, Ann M.; Toto, Tami; ...

2015-06-19

Observation-based modeling case studies of continental boundary layer clouds have been developed to study cloudy boundary layers, aerosol influences upon them, and their representation in cloud- and global-scale models. Three 60-hour case study periods span the temporal evolution of cumulus, stratiform, and drizzling boundary layer cloud systems, representing mixed and transitional states rather than idealized or canonical cases. Based on in-situ measurements from the RACORO field campaign and remote-sensing observations, the cases are designed with a modular configuration to simplify use in large-eddy simulations (LES) and single-column models. Aircraft measurements of aerosol number size distribution are fit to lognormal functionsmore » for concise representation in models. Values of the aerosol hygroscopicity parameter, κ, are derived from observations to be ~0.10, which are lower than the 0.3 typical over continents and suggestive of a large aerosol organic fraction. Ensemble large-scale forcing datasets are derived from the ARM variational analysis, ECMWF forecasts, and a multi-scale data assimilation system. The forcings are assessed through comparison of measured bulk atmospheric and cloud properties to those computed in 'trial' large-eddy simulations, where more efficient run times are enabled through modest reductions in grid resolution and domain size compared to the full-sized LES grid. Simulations capture many of the general features observed, but the state-of-the-art forcings were limited at representing details of cloud onset, and tight gradients and high-resolution transients of importance. Methods for improving the initial conditions and forcings are discussed. The cases developed are available to the general modeling community for studying continental boundary clouds.« less

Horizon as critical phenomenon

NASA Astrophysics Data System (ADS)

Lee, Sung-Sik

2016-09-01

We show that renormalization group flow can be viewed as a gradual wave function collapse, where a quantum state associated with the action of field theory evolves toward a final state that describes an IR fixed point. The process of collapse is described by the radial evolution in the dual holographic theory. If the theory is in the same phase as the assumed IR fixed point, the initial state is smoothly projected to the final state. If in a different phase, the initial state undergoes a phase transition which in turn gives rise to a horizon in the bulk geometry. We demonstrate the connection between critical behavior and horizon in an example, by deriving the bulk metrics that emerge in various phases of the U( N ) vector model in the large N limit based on the holographic dual constructed from quantum renormalization group. The gapped phase exhibits a geometry that smoothly ends at a finite proper distance in the radial direction. The geometric distance in the radial direction measures a complexity: the depth of renormalization group transformation that is needed to project the generally entangled UV state to a direct product state in the IR. For gapless states, entanglement persistently spreads out to larger length scales, and the initial state can not be projected to the direct product state. The obstruction to smooth projection at charge neutral point manifests itself as the long throat in the anti-de Sitter space. The Poincare horizon at infinity marks the critical point which exhibits a divergent length scale in the spread of entanglement. For the gapless states with non-zero chemical potential, the bulk space becomes the Lifshitz geometry with the dynamical critical exponent two. The identification of horizon as critical point may provide an explanation for the universality of horizon. We also discuss the structure of the bulk tensor network that emerges from the quantum renormalization group.

Inhomogeneities and superconductivity in poly-phase Fe-Se-Te systems

NASA Astrophysics Data System (ADS)

Hartwig, S.; Schäfer, N.; Schulze, M.; Landsgesell, S.; Abou-Ras, D.; Blum, Ch. G. F.; Wurmehl, S.; Sokolowski, A.; Büchner, B.; Prokeš, K.

2018-02-01

The impact of synthesis conditions, post-preparation heating procedure, aging and influence of pressure on the superconducting properties of FeSe0.4Te0.6 crystals is reported. Two FeSe0.4Te0.6 single crystals were used in the study, prepared from stoichiometric melt but cooled down with very different cooling rates, and investigated using magnetic bulk and electrical-resistivity methods. The fast-cooled crystal contains large inclusions of Fe3Se2.1Te1.8 and exhibits bulk superconductivity in its as-prepared state, while the other is homogeneous and shows only traces of superconductivity. AC susceptibility measurements under hydrostatic pressure show that the superconducting transition temperature of the inhomogeneous crystal increases from 12.3 K at ambient pressure to Tsc = 17.9 K at 9 kbar. On the other hand, neither pressure nor mechanically-induced stress is sufficient to induce superconductivity in the homogeneous crystal. However, an additional heat treatment at 673 K followed by fast cooling down and/or long-term aging at ambient conditions leads to the appearance of bulk superconductivity also in the latter sample. This sample remains homogeneous on a scale down to few μm but shows an additional magnetic phase transition around 130 K suggesting that it must be inhomogeneous. For comparison also Fe3Se2.1Te1.8 polycrystals have been prepared and their magnetic properties have been studied. It appears that this phase is not superconducting by itself. It is concluded that nano-scale inhomogeneities that appear in the FeSexTe1-x system due to a spinodal decomposition in the solid state are necessary for bulk superconductivity, possibly due to minor changes in the crystal structure and microstructure. Macroscopic inclusions quenched by fast cooling from high temperatures lead obviously to strain and hence variations in the lattice constants, an effect that is further supported by application of pressure/stress.

Numerical investigations on flow dynamics of prismatic granular materials using the discrete element method

NASA Astrophysics Data System (ADS)

Hancock, W.; Weatherley, D.; Wruck, B.; Chitombo, G. P.

2012-04-01

The flow dynamics of granular materials is of broad interest in both the geosciences (e.g. landslides, fault zone evolution, and brecchia pipe formation) and many engineering disciplines (e.g chemical engineering, food sciences, pharmaceuticals and materials science). At the interface between natural and human-induced granular media flow, current underground mass-mining methods are trending towards the induced failure and subsequent gravitational flow of large volumes of broken rock, a method known as cave mining. Cave mining relies upon the undercutting of a large ore body, inducement of fragmentation of the rock and subsequent extraction of ore from below, via hopper-like outlets. Design of such mines currently relies upon a simplified kinematic theory of granular flow in hoppers, known as the ellipsoid theory of mass movement. This theory assumes that the zone of moving material grows as an ellipsoid above the outlet of the silo. The boundary of the movement zone is a shear band and internal to the movement zone, the granular material is assumed to have a uniformly high bulk porosity compared with surrounding stagnant regions. There is however, increasing anecdotal evidence and field measurements suggesting this theory fails to capture the full complexity of granular material flow within cave mines. Given the practical challenges obstructing direct measurement of movement both in laboratory experiments and in-situ, the Discrete Element Method (DEM [1]) is a popular alternative to investigate granular media flow. Small-scale DEM studies (c.f. [3] and references therein) have confirmed that movement within DEM silo flow models matches that predicted by ellipsoid theory, at least for mono-disperse granular material freely outflowing at a constant rate. A major draw-back of these small-scale DEM studies is that the initial bulk porosity of the simulated granular material is significantly higher than that of broken, prismatic rock. In this investigation, more realistic granular material geometries are simulated using the ESyS-Particle [2] DEM simulation software on cluster supercomputers. Individual grains of the granular material are represented as convex polyhedra. Initially the polyhedra are packed in a low bulk porosity configuration prior to commencing silo flow simulations. The resultant flow dynamics are markedly different to that predicted by ellipsoid theory. Initially shearing occurs around the silo outlet however rapidly shear localization in a particular direction dominates other directions, causing preferential movement in that direction. Within the shear band itself, the granular material becomes hgihly dilated however elsewhere the bulk porosity remains low. The low porosity within these regions promotes entrainment whereby large volumes of granular material interlock and begin to rotate and translate as a single rigid body. In some cases, entrainment may result in complete overturning of a large volume of material. The consequences of preferential shear localization and in particular, entrainment, for granular media flow in cave mines and natural settings (such as brecchia pipes) is a topic of ongoing research to be presented at the meeting.

High-Fat, High-Sugar Diet-Induced Subendothelial Matrix Stiffening is Mitigated by Exercise.

PubMed

Kohn, Julie C; Azar, Julian; Seta, Francesca; Reinhart-King, Cynthia A

2018-03-01

Consumption of a high-fat, high-sugar diet and sedentary lifestyle are correlated with bulk arterial stiffening. While measurements of bulk arterial stiffening are used to assess cardiovascular health clinically, they cannot account for changes to the tissue occurring on the cellular scale. The compliance of the subendothelial matrix in the intima mediates vascular permeability, an initiating step in atherosclerosis. High-fat, high-sugar diet consumption and a sedentary lifestyle both cause micro-scale subendothelial matrix stiffening, but the impact of these factors in concert remains unknown. In this study, mice on a high-fat, high-sugar diet were treated with aerobic exercise or returned to a normal diet. We measured bulk arterial stiffness through pulse wave velocity and subendothelial matrix stiffness ex vivo through atomic force microscopy. Our data indicate that while diet reversal mitigates high-fat, high-sugar diet-induced macro- and micro-scale stiffening, exercise only significantly decreases micro-scale stiffness and not macro-scale stiffness, during the time-scale studied. These data underscore the need for both healthy diet and exercise to maintain vascular health. These data also indicate that exercise may serve as a key lifestyle modification to partially reverse the deleterious impacts of high-fat, high-sugar diet consumption, even while macro-scale stiffness indicators do not change.

Thermal hazard assessment of AN and AN-based explosives.

PubMed

Turcotte, R; Lightfoot, P D; Fouchard, R; Jones, D E G

2003-07-04

Ammonium nitrate (AN) is an essential ingredient in most fertilizers. It is also widely used in the commercial explosives industry. In this latter application, it is mostly mixed with fuel oil to form the most popular commercial explosive: ANFO. In both the fertilizer and the explosive industry, aqueous AN solutions (ANS) of various concentrations are processed. These solutions also form the basis of ammonium nitrate emulsion explosives (also called ammonium nitrate emulsions or ANE), which are produced either in bulk or in packaged form. For all these AN-based products, quantities of the order of 20,000kg are being manufactured, transported, stored, and processed at elevated temperatures and/or elevated pressures. Correspondingly, major accidents involving overheating of large quantities of these products have happened in several of these operations. In comparison, convenient laboratory quantities to investigate thermal decomposition properties are generally less than 1kg. As a result, in order to provide information applicable to real-life situations, any laboratory study must use techniques that minimize heat losses from the samples to their environment. In the present study, two laboratory-scale calorimeters providing an adiabatic environment were used: an accelerating rate calorimeter (ARC) and an adiabatic Dewar calorimeter (ADC). Experiments were performed on pure AN, ANFO, various ANS systems, and typical bulk and packaged ANE systems. The effects of sample mass, atmosphere, and formulation on the resulting onset temperatures were studied. A comparison of the results from the two techniques is provided and a proposed method to extrapolate these results to large-scale inventories is examined.

Beer tapping: dynamics of bubbles after impact

NASA Astrophysics Data System (ADS)

Mantič-Lugo, V.; Cayron, A.; Brun, P.-T.; Gallaire, F.

2015-12-01

Beer tapping is a well known prank where a bottle of beer is impacted from the top by a solid object, usually another bottle, leading to a sudden foam overflow. A description of the shock-driven bubble dynamics leading to foaming is presented based on an experimental and numerical study evoking the following physical picture. First, the solid impact produces a sudden downwards acceleration of the bottle creating a strong depression in the liquid bulk. The existing bubbles undergo a strong expansion and a sudden contraction ending in their collapse and fragmentation into a large amount of small bubbles. Second, the bubble clouds present a large surface area to volume ratio, enhancing the CO2 diffusion from the supersaturated liquid, hence growing rapidly and depleting the CO2. The clouds of bubbles migrate upwards in the form of plumes pulling the surrounding liquid with them and eventually resulting in the foam overflow. The sudden pressure drop that triggers the bubble dynamics with a collapse and oscillations is modelled by the Rayleigh-Plesset equation. The bubble dynamics from impact to collapse occurs over a time (tb ≃ 800 μs) much larger than the acoustic time scale of the liquid bulk (tac = 2H/c ≃ 80 μs), for the experimental container of height H = 6 cm and a speed of sound around c ≃ 1500 m/s. This scale separation, together with the comparison of numerical and experimental results, suggests that the pressure drop is controlled by two parameters: the acceleration of the container and the distance from the bubble to the free surface.

The ''self-stirred'' genome: Bulk and surface dynamics of the chromatin globule

NASA Astrophysics Data System (ADS)

Zidovska, Alexandra

Chromatin structure and dynamics control all aspects of DNA biology yet are poorly understood. In interphase, time between two cell divisions, chromatin fills the cell nucleus in its minimally condensed polymeric state. Chromatin serves as substrate to a number of biological processes, e.g. gene expression and DNA replication, which require it to become locally restructured. These are energy-consuming processes giving rise to non-equilibrium dynamics. Chromatin dynamics has been traditionally studied by imaging of fluorescently labeled nuclear proteins and single DNA-sites, thus focusing only on a small number of tracer particles. Recently, we developed an approach, displacement correlation spectroscopy (DCS) based on time-resolved image correlation analysis, to map chromatin dynamics simultaneously across the whole nucleus in cultured human cells. DCS revealed that chromatin movement was coherent across large regions (4-5 μm) for several seconds. Regions of coherent motion extended beyond the boundaries of single-chromosome territories, suggesting elastic coupling of motion over length scales much larger than those of genes. These large-scale, coupled motions were ATP-dependent and unidirectional for several seconds. Following these observations, we developed a hydrodynamic theory of active chromatin dynamics, using the two-fluid model and describing the content of cell nucleus as a chromatin solution, which is subject to both passive thermal fluctuations and active (ATP-consuming) scalar and vector events. In this work we continue in our efforts to elucidate the mechanism and function of the chromatin dynamics in interphase. We investigate the chromatin interactions with the nuclear envelope and compare the surface dynamics of the chromatin globule with its bulk dynamics.

Scaling analysis of cloud and rain water in marine stratocumulus and implications for scale-aware microphysical parameterizations

NASA Astrophysics Data System (ADS)

Witte, M.; Morrison, H.; Jensen, J. B.; Bansemer, A.; Gettelman, A.

2017-12-01

The spatial covariance of cloud and rain water (or in simpler terms, small and large drops, respectively) is an important quantity for accurate prediction of the accretion rate in bulk microphysical parameterizations that account for subgrid variability using assumed probability density functions (pdfs). Past diagnoses of this covariance from remote sensing, in situ measurements and large eddy simulation output have implicitly assumed that the magnitude of the covariance is insensitive to grain size (i.e. horizontal resolution) and averaging length, but this is not the case because both cloud and rain water exhibit scale invariance across a wide range of scales - from tens of centimeters to tens of kilometers in the case of cloud water, a range that we will show is primarily limited by instrumentation and sampling issues. Since the individual variances systematically vary as a function of spatial scale, it should be expected that the covariance follows a similar relationship. In this study, we quantify the scaling properties of cloud and rain water content and their covariability from high frequency in situ aircraft measurements of marine stratocumulus taken over the southeastern Pacific Ocean aboard the NSF/NCAR C-130 during the VOCALS-REx field experiment of October-November 2008. First we confirm that cloud and rain water scale in distinct manners, indicating that there is a statistically and potentially physically significant difference in the spatial structure of the two fields. Next, we demonstrate that the covariance is a strong function of spatial scale, which implies important caveats regarding the ability of limited-area models with domains smaller than a few tens of kilometers across to accurately reproduce the spatial organization of precipitation. Finally, we present preliminary work on the development of a scale-aware parameterization of cloud-rain water subgrid covariability based in multifractal analysis intended for application in large-scale model microphysics schemes.

Carbon diffusion in bulk hcp zirconium: A multi-scale approach

NASA Astrophysics Data System (ADS)

Xu, Y.; Roques, J.; Domain, C.; Simoni, E.

2016-05-01

In the framework of the geological repository of the used fuel claddings of pressurized water reactor, carbon behavior in bulk zirconium is studied by periodic Density Functional Theory calculations. The C interstitial sites were investigated and it was found that there are two possible carbon interstitial sites: a distorted basal tetragonal site and an octahedral site. There are four types of possible atomic jumps between them. After calculating the migration energies, the attempt frequencies and the jump probabilities for each possible migration path, kinetic Monte Carlo (KMC) simulations were performed to simulate carbon diffusion at the macroscopic scale. The results show that carbon diffusion in pure Zr bulk is extremely limited at the storage temperature (50 °C). Since there are defects in Zr bulk, in a second step, the effect of atomic vacancy was studied and it was proved that vacancies cannot increase carbon diffusion.

Nontrivial behavior of water in the vicinity and inside lipid bilayers as probed by molecular dynamics simulations.

PubMed

Krylov, Nikolay A; Pentkovsky, Vladimir M; Efremov, Roman G

2013-10-22

The atomic-scale diffusion of water in the presence of several lipid bilayers mimicking biomembranes is characterized via unconstrained molecular dynamics (MD) simulations. Although the overall water dynamics corresponds well to literature data, namely, the efficient braking near polar head groups of lipids, a number of interesting and biologically relevant details observed in this work have not been sufficiently discussed so far; for instance, the fact that waters "sense" the membrane unexpectedly early, before water density begins to decrease. In this "transitional zone" the velocity distributions of water and their H-bonding patterns deviate from those in the bulk solution. The boundaries of this zone are well preserved even despite the local (<1 nm size) perturbation of the lipid bilayer, thus indicating a decoupling of the surface and bulk dynamics of water. This is in excellent agreement with recent experimental data. Near the membrane surface, water movement becomes anisotropic, that is, solvent molecules preferentially move outward the bilayer. Deep in the membrane interior, the velocities can even exceed those in the bulk solvent and undergo large-scale fluctuations. The analysis of MD trajectories of individual waters in the middle part of the acyl chain region of lipids reveals a number of interesting rare phenomena, such as the fast (ca. 50 ps) breakthrough across the membrane or long-time (up to 750 ps) "roaming" between lipid leaflets. The analysis of these events was accomplished to delineate the mechanisms of spontaneous water permeation inside the hydrophobic membrane core. It was shown that such nontrivial dynamics of water in an "alien" environment is driven by the dynamic heterogeneities of the local bilayer structure and the formation of transient atomic-scale "defects" in it. The picture observed in lipid bilayers is drastically different from that in a primitive membrane mimic, a hydrated cyclohexane slab. The possible biological impact of such phenomena in equilibrated lipid bilayers is discussed.

Bacterial toxicity comparison between nano- and micro-scaled oxide particles.

PubMed

Jiang, Wei; Mashayekhi, Hamid; Xing, Baoshan

2009-05-01

Toxicity of nano-scaled aluminum, silicon, titanium and zinc oxides to bacteria (Bacillus subtilis, Escherichia coli and Pseudomonas fluorescens) was examined and compared to that of their respective bulk (micro-scaled) counterparts. All nanoparticles but titanium oxide showed higher toxicity (at 20 mg/L) than their bulk counterparts. Toxicity of released metal ions was differentiated from that of the oxide particles. ZnO was the most toxic among the three nanoparticles, causing 100% mortality to the three tested bacteria. Al(2)O(3) nanoparticles had a mortality rate of 57% to B. subtilis, 36% to E. coli, and 70% to P. fluorescens. SiO(2) nanoparticles killed 40% of B. subtilis, 58% of E. coli, and 70% of P. fluorescens. TEM images showed attachment of nanoparticles to the bacteria, suggesting that the toxicity was affected by bacterial attachment. Bacterial responses to nanoparticles were different from their bulk counterparts; hence nanoparticle toxicity mechanisms need to be studied thoroughly.

Long-term spatial and temporal microbial community dynamics in a large-scale drinking water distribution system with multiple disinfectant regimes.

PubMed

Potgieter, Sarah; Pinto, Ameet; Sigudu, Makhosazana; du Preez, Hein; Ncube, Esper; Venter, Stephanus

2018-08-01

Long-term spatial-temporal investigations of microbial dynamics in full-scale drinking water distribution systems are scarce. These investigations can reveal the process, infrastructure, and environmental factors that influence the microbial community, offering opportunities to re-think microbial management in drinking water systems. Often, these insights are missed or are unreliable in short-term studies, which are impacted by stochastic variabilities inherent to large full-scale systems. In this two-year study, we investigated the spatial and temporal dynamics of the microbial community in a large, full scale South African drinking water distribution system that uses three successive disinfection strategies (i.e. chlorination, chloramination and hypochlorination). Monthly bulk water samples were collected from the outlet of the treatment plant and from 17 points in the distribution system spanning nearly 150 km and the bacterial community composition was characterised by Illumina MiSeq sequencing of the V4 hypervariable region of the 16S rRNA gene. Like previous studies, Alpha- and Betaproteobacteria dominated the drinking water bacterial communities, with an increase in Betaproteobacteria post-chloramination. In contrast with previous reports, the observed richness, diversity, and evenness of the bacterial communities were higher in the winter months as opposed to the summer months in this study. In addition to temperature effects, the seasonal variations were also likely to be influenced by changes in average water age in the distribution system and corresponding changes in disinfectant residual concentrations. Spatial dynamics of the bacterial communities indicated distance decay, with bacterial communities becoming increasingly dissimilar with increasing distance between sampling locations. These spatial effects dampened the temporal changes in the bulk water community and were the dominant factor when considering the entire distribution system. However, temporal variations were consistently stronger as compared to spatial changes at individual sampling locations and demonstrated seasonality. This study emphasises the need for long-term studies to comprehensively understand the temporal patterns that would otherwise be missed in short-term investigations. Furthermore, systematic long-term investigations are particularly critical towards determining the impact of changes in source water quality, environmental conditions, and process operations on the changes in microbial community composition in the drinking water distribution system. Copyright © 2018 Elsevier Ltd. All rights reserved.

Teaching machines to find mantle composition

NASA Astrophysics Data System (ADS)

Atkins, Suzanne; Tackley, Paul; Trampert, Jeannot; Valentine, Andrew

2017-04-01

The composition of the mantle affects many geodynamical processes by altering factors such as the density, the location of phase changes, and melting temperature. The inferences we make about mantle composition also determine how we interpret the changes in velocity, reflections, attenuation and scattering seen by seismologists. However, the bulk composition of the mantle is very poorly constrained. Inferences are made from meteorite samples, rock samples from the Earth and inferences made from geophysical data. All of these approaches require significant assumptions and the inferences made are subject to large uncertainties. Here we present a new method for inferring mantle composition, based on pattern recognition machine learning, which uses large scale in situ observations of the mantle to make fully probabilistic inferences of composition for convection simulations. Our method has an advantage over other petrological approaches because we use large scale geophysical observations. This means that we average over much greater length scales and do not need to rely on extrapolating from localised samples of the mantle or planetary disk. Another major advantage of our method is that it is fully probabilistic. This allows us to include all of the uncertainties inherent in the inference process, giving us far more information about the reliability of the result than other methods. Finally our method includes the impact of composition on mantle convection. This allows us to make much more precise inferences from geophysical data than other geophysical approaches, which attempt to invert one observation with no consideration of the relationship between convection and composition. We use a sampling based inversion method, using hundreds of convection simulations run using StagYY with self consistent mineral physics properties calculated using the PerpleX package. The observations from these simulations are used to train a neural network to make a probabilistic inference for major element oxide composition of the mantle. We find we can constrain bulk mantle FeO molar percent, FeO/MgO and FeO/SiO2 using observations of the temperature and density structure of the mantle in convection simulations.

From Fibrils to Toughness: Multi-Scale Mechanics of Fibrillating Interfaces in Stretchable Electronics

PubMed Central

van der Sluis, Olaf; Vossen, Bart; Geers, Marc

2018-01-01

Metal-elastomer interfacial systems, often encountered in stretchable electronics, demonstrate remarkably high interface fracture toughness values. Evidently, a large gap exists between the rather small adhesion energy levels at the microscopic scale (‘intrinsic adhesion’) and the large measured macroscopic work-of-separation. This energy gap is closed here by unravelling the underlying dissipative mechanisms through a systematic numerical/experimental multi-scale approach. This self-containing contribution collects and reviews previously published results and addresses the remaining open questions by providing new and independent results obtained from an alternative experimental set-up. In particular, the experimental studies on Cu-PDMS (Poly(dimethylsiloxane)) samples conclusively reveal the essential role of fibrillation mechanisms at the micro-meter scale during the metal-elastomer delamination process. The micro-scale numerical analyses on single and multiple fibrils show that the dynamic release of the stored elastic energy by multiple fibril fracture, including the interaction with the adjacent deforming bulk PDMS and its highly nonlinear behaviour, provide a mechanistic understanding of the high work-of-separation. An experimentally validated quantitative relation between the macroscopic work-of-separation and peel front height is established from the simulation results. Finally, it is shown that a micro-mechanically motivated shape of the traction-separation law in cohesive zone models is essential to describe the delamination process in fibrillating metal-elastomer systems in a physically meaningful way. PMID:29393908

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1990-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T (sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1989-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T(sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

Cosmic bulk flow and the local motion from Cosmicflows-2

NASA Astrophysics Data System (ADS)

Hoffman, Yehuda; Courtois, Hélène M.; Tully, R. Brent

2015-06-01

Full sky surveys of peculiar velocity are arguably the best way to map the large-scale structure (LSS) out to distances of a few × 100 h-1 Mpc. Using the largest and most accurate ever catalogue of galaxy peculiar velocities Cosmicflows-2, the LSS has been reconstructed by means of the Wiener filter (WF) and constrained realizations (CRs) assuming as a Bayesian prior model the Λ cold dark matter model with the WMAP inferred cosmological parameters. This paper focuses on studying the bulk flow of the local flow field, defined as the mean velocity of top-hat spheres with radii ranging out to R = 500 h-1 Mpc. The estimated LSS, in general, and the bulk flow, in particular, are determined by the tension between the observational data and the assumed prior model. A pre-requisite for such an analysis is the requirement that the estimated bulk flow is consistent with the prior model. Such a consistency is found here. At R = 50 (150) h-1 Mpc, the estimated bulk velocity is 250 ± 21 (239 ± 38) km s-1. The corresponding cosmic variance at these radii is 126 (60) km s-1, which implies that these estimated bulk flows are dominated by the data and not by the assumed prior model. The estimated bulk velocity is dominated by the data out to R ≈ 200 h-1 Mpc, where the cosmic variance on the individual supergalactic Cartesian components (of the rms values) exceeds the variance of the CRs by at least a factor of 2. The SGX and SGY components of the cosmic microwave background dipole velocity are recovered by the WF velocity field down to a very few km s-1. The SGZ component of the estimated velocity, the one that is most affected by the zone of avoidance, is off by 126 km s-1 (an almost 2σ discrepancy). The bulk velocity analysis reported here is virtually unaffected by the Malmquist bias and very similar results are obtained for the data with and without the bias correction.

Effect of graphene layer thickness and mechanical compliance on interfacial heat flow and thermal conduction in solid-liquid phase change materials.

PubMed

Warzoha, Ronald J; Fleischer, Amy S

2014-08-13

Solid-liquid phase change materials (PCMs) are attractive candidates for thermal energy storage and electronics cooling applications but have limited applicability in state-of-the-art technologies due to their low intrinsic thermal conductivities. Recent efforts to incorporate graphene and multilayer graphene into PCMs have led to the development of thermal energy storage materials with remarkable values of bulk thermal conductivity. However, the full potential of graphene as a filler material for the thermal enhancement of PCMs remains unrealized, largely due to an incomplete understanding of the physical mechanisms that govern thermal transport within graphene-based nanocomposites. In this work, we show that the number of graphene layers (n) within an individual graphene nanoparticle has a significant effect on the bulk thermal conductivity of an organic PCM. Results indicate that the bulk thermal conductivity of PCMs can be tuned by over an order of magnitude simply by adjusting the number of graphene layers (n) from n = 3 to 44. Using scanning electron microscopy in tandem with nanoscale analytical techniques, the physical mechanisms that govern heat flow within a graphene nanocomposite PCM are found to be nearly independent of the intrinsic thermal conductivity of the graphene nanoparticle itself and are instead found to be dependent on the mechanical compliance of the graphene nanoparticles. These findings are critical for the design and development of PCMs that are capable of cooling next-generation electronics and storing heat effectively in medium-to-large-scale energy systems, including solar-thermal power plants and building heating and cooling systems.

Multi-Product Microalgae Biorefineries: From Concept Towards Reality.

PubMed

't Lam, G P; Vermuë, M H; Eppink, M H M; Wijffels, R H; van den Berg, C

2018-02-01

Although microalgae are a promising biobased feedstock, industrial scale production is still far off. To enhance the economic viability of large-scale microalgae processes, all biomass components need to be valorized, requiring a multi-product biorefinery. However, this concept is still too expensive. Typically, downstream processing of industrial biotechnological bulk products accounts for 20-40% of the total production costs, while for a microalgae multi-product biorefinery the costs are substantially higher (50-60%). These costs are high due to the lack of appropriate and mild technologies to access the different product fractions such as proteins, carbohydrates, and lipids. To reduce the costs, simplified processes need to be developed for the main unit operations including harvesting, cell disruption, extraction, and possibly fractionation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reactor concepts for bioelectrochemical syntheses and energy conversion.

PubMed

Krieg, Thomas; Sydow, Anne; Schröder, Uwe; Schrader, Jens; Holtmann, Dirk

2014-12-01

In bioelectrochemical systems (BESs) at least one electrode reaction is catalyzed by microorganisms or isolated enzymes. One of the existing challenges for BESs is shifting the technology towards industrial use and engineering reactor systems at adequate scales. Due to the fact that most BESs are usually deployed in the production of large-volume but low-value products (e.g., energy, fuels, and bulk chemicals), investment and operating costs must be minimized. Recent advances in reactor concepts for different BESs, in particular biofuel cells and electrosynthesis, are summarized in this review including electrode development and first applications on a technical scale. A better understanding of the impact of reactor components on the performance of the reaction system is an important step towards commercialization of BESs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Large-Scale Surfactant-Free Synthesis of p-Type SnTe Nanoparticles for Thermoelectric Applications

PubMed Central

Han, Guang; Zhang, Ruizhi; Popuri, Srinivas R.; Greer, Heather F.; Reece, Michael J.; Bos, Jan-Willem G.; Zhou, Wuzong; Knox, Andrew R.; Gregory, Duncan H.

2017-01-01

A facile one-pot aqueous solution method has been developed for the fast and straightforward synthesis of SnTe nanoparticles in more than ten gram quantities per batch. The synthesis involves boiling an alkaline Na2SnO2 solution and a NaHTe solution for short time scales, in which the NaOH concentration and reaction duration play vital roles in controlling the phase purity and particle size, respectively. Spark plasma sintering of the SnTe nanoparticles produces nanostructured compacts that have a comparable thermoelectric performance to bulk counterparts synthesised by more time- and energy-intensive methods. This approach, combining an energy-efficient, surfactant-free solution synthesis with spark plasma sintering, provides a simple, rapid, and inexpensive route to p-type SnTe nanostructured materials. PMID:28772593

Magnetic Reconnection and Particle Acceleration in the Solar Corona

NASA Astrophysics Data System (ADS)

Neukirch, Thomas

Reconnection plays a major role for the magnetic activity of the solar atmosphere, for example solar flares. An interesting open problem is how magnetic reconnection acts to redistribute the stored magnetic energy released during an eruption into other energy forms, e.g. gener-ating bulk flows, plasma heating and non-thermal energetic particles. In particular, finding a theoretical explanation for the observed acceleration of a large number of charged particles to high energies during solar flares is presently one of the most challenging problems in solar physics. One difficulty is the vast difference between the microscopic (kinetic) and the macro-scopic (MHD) scales involved. Whereas the phenomena observed to occur on large scales are reasonably well explained by the so-called standard model, this does not seem to be the case for the small-scale (kinetic) aspects of flares. Over the past years, observations, in particular by RHESSI, have provided evidence that a naive interpretation of the data in terms of the standard solar flare/thick target model is problematic. As a consequence, the role played by magnetic reconnection in the particle acceleration process during solar flares may have to be reconsidered.

Vibrational density of states and thermodynamics at the nanoscale: the 3D-2D transition in gold nanostructures

PubMed Central

Carles, R.; Benzo, P.; Pécassou, B.; Bonafos, C.

2016-01-01

Surface enhanced Raman scattering (SERS) is generally and widely used to enhance the vibrational fingerprint of molecules located at the vicinity of noble metal nanoparticles. In this work, SERS is originally used to enhance the own vibrational density of states (VDOS) of nude and isolated gold nanoparticles. This offers the opportunity of analyzing finite size effects on the lattice dynamics which remains unattainable with conventional techniques based on neutron or x-ray inelastic scattering. By reducing the size down to few nanometers, the role of surface atoms versus volume atoms become dominant, and the “text-book” 3D-2D transition on the dynamical behavior is experimentally emphasized. “Anomalies” that have been predicted by a large panel of simulations at the atomic scale, are really observed, like the enhancement of the VDOS at low frequencies or the occurrence of localized modes at frequencies beyond the cut-off in bulk. Consequences on the thermodynamic properties at the nanoscale, like the reduction of the Debye temperature or the excess of the specific heat, have been evaluated. Finally the high sensitivity of reminiscent bulk-like phonons on the arrangements at the atomic scale is used to access the morphology and internal disorder of the nanoparticles. PMID:27982080

Vibrational density of states and thermodynamics at the nanoscale: the 3D-2D transition in gold nanostructures

NASA Astrophysics Data System (ADS)

Carles, R.; Benzo, P.; Pécassou, B.; Bonafos, C.

2016-12-01

Surface enhanced Raman scattering (SERS) is generally and widely used to enhance the vibrational fingerprint of molecules located at the vicinity of noble metal nanoparticles. In this work, SERS is originally used to enhance the own vibrational density of states (VDOS) of nude and isolated gold nanoparticles. This offers the opportunity of analyzing finite size effects on the lattice dynamics which remains unattainable with conventional techniques based on neutron or x-ray inelastic scattering. By reducing the size down to few nanometers, the role of surface atoms versus volume atoms become dominant, and the “text-book” 3D-2D transition on the dynamical behavior is experimentally emphasized. “Anomalies” that have been predicted by a large panel of simulations at the atomic scale, are really observed, like the enhancement of the VDOS at low frequencies or the occurrence of localized modes at frequencies beyond the cut-off in bulk. Consequences on the thermodynamic properties at the nanoscale, like the reduction of the Debye temperature or the excess of the specific heat, have been evaluated. Finally the high sensitivity of reminiscent bulk-like phonons on the arrangements at the atomic scale is used to access the morphology and internal disorder of the nanoparticles.

Two-dimensional topological insulators with large bulk energy gap

NASA Astrophysics Data System (ADS)

Yang, Z. Q.; Jia, Jin-Feng; Qian, Dong

2016-11-01

Two-dimensional (2D) topological insulators (TIs, or quantum spin Hall insulators) are special insulators that possess bulk 2D electronic energy gap and time-reversal symmetry protected one-dimensional (1D) edge state. Carriers in the edge state have the property of spin-momentum locking, enabling dissipation-free conduction along the 1D edge. The existence of 2D TIs was confirmed by experiments in semiconductor quantum wells. However, the 2D bulk gaps in those quantum wells are extremely small, greatly limiting potential application in future electronics and spintronics. Despite this limitation, 2D TIs with a large bulk gap attracted plenty of interest. In this paper, recent progress in searching for TIs with a large bulk gap is reviewed briefly. We start by introducing some theoretical predictions of these new materials and then discuss some recent important achievements in crystal growth and characterization. Project supported by the National Natural Science Foundation of China (Grant Nos. U1632272, 11574201, and 11521404). D. Q. acknowledges support from the Changjiang Scholars Program, China and the Program for Professor of Special Appointment (Eastern Scholar), China.

The influence of surfactant on the propagation of a semi-infinite bubble through a liquid-filled compliant channel

PubMed Central

Halpern, David; Gaver, Donald P.

2012-01-01

We investigate the influence of a soluble surfactant on the steady-state motion of a finger of air through a compliant channel. This study provides a basic model from which to understand the fluid–structure interactions and physicochemical hydrodynamics of pulmonary airway reopening. Airway closure occurs in lung diseases such as respiratory distress syndrome and acute respiratory distress syndrome as a result of fluid accumulation and surfactant insufficiency. This results in ‘compliant collapse’ with the airway walls buckled and held in apposition by a liquid occlusion that blocks the passage of air. Airway reopening is essential to the recovery of adequate ventilation, but has been associated with ventilator-induced lung injury because of the exposure of airway epithelial cells to large interfacial flow-induced pressure gradients. Surfactant replacement is helpful in modulating this deleterious mechanical stimulus, but is limited in its effectiveness owing to slow surfactant adsorption. We investigate the effect of surfactant on micro-scale models of reopening by computationally modelling the steady two-dimensional motion of a semi-infinite bubble propagating through a liquid-filled compliant channel doped with soluble surfactant. Many dimensionless parameters affect reopening, but we primarily investigate how the reopening pressure pb depends upon the capillary number Ca (the ratio of viscous to surface tension forces), the adsorption depth parameter λ (a bulk concentration parameter) and the bulk Péclet number Peb (the ratio of bulk convection to diffusion). These studies demonstrate a dependence of pb on λ, and suggest that a critical bulk concentration must be exceeded to operate as a low-surface-tension system. Normal and tangential stress gradients remain largely unaffected by physicochemical interactions – for this reason, further biological studies are suggested that will clarify the role of wall flexibility and surfactant on the protection of the lung from atelectrauma. PMID:22997476

Bounds for OPE coefficients on the Regge trajectory

NASA Astrophysics Data System (ADS)

Costa, Miguel S.; Hansen, Tobias; Penedones, João

2017-10-01

We consider the Regge limit of the CFT correlation functions < JJOO> and < TTOO>, where J is a vector current, T is the stress tensor and O is some scalar operator. These correlation functions are related by a type of Fourier transform to the AdS phase shift of the dual 2-to-2 scattering process. AdS unitarity was conjectured some time ago to be positivity of the imaginary part of this bulk phase shift. This condition was recently proved using purely CFT arguments. For large N CFTs we further expand on these ideas, by considering the phase shift in the Regge limit, which is dominated by the leading Regge pole with spin j( ν), where ν is a spectral parameter. We compute the phase shift as a function of the bulk impact parameter, and then use AdS unitarity to impose bounds on the analytically continued OPE coefficients {C}_JJ}j(ν )} and C TTj(ν) that describe the coupling to the leading Regge trajectory of the current J and stress tensor T. AdS unitarity implies that the OPE coefficients associated to non-minimal couplings of the bulk theory vanish at the intercept value ν = 0, for any CFT. Focusing on the case of large gap theories, this result can be used to show that the physical OPE coefficients {C}_{JJT and C TTT , associated to non-minimal bulk couplings, scale with the gap Δ g as Δ g - 2 or Δ g - 4 . Also, looking directly at the unitarity condition imposed at the OPE coefficients {C_JJT and C TTT results precisely in the known conformal collider bounds, giving a new CFT derivation of these bounds. We finish with remarks on finite N theories and show directly in the CFT that the spin function j( ν) is convex, extending this property to the continuation to complex spin.

Hidden cycle of dissolved organic carbon in the deep ocean.

PubMed

Follett, Christopher L; Repeta, Daniel J; Rothman, Daniel H; Xu, Li; Santinelli, Chiara

2014-11-25

Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ(13)C and age via Δ(14)C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle.

Hidden cycle of dissolved organic carbon in the deep ocean

PubMed Central

Follett, Christopher L.; Repeta, Daniel J.; Rothman, Daniel H.; Xu, Li; Santinelli, Chiara

2014-01-01

Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ13C and age via Δ14C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle. PMID:25385632

Tensile Fracture of Welded Polymer Interfaces: Miscibility, Entanglements, and Crazing

DOE PAGES

Ge, Ting; Grest, Gary S.; Robbins, Mark O.

2014-09-26

Large-scale molecular simulations are performed to investigate tensile failure of polymer interfaces as a function of welding time t. Changes in the tensile stress, mode of failure and interfacial fracture energy G I are correlated to changes in the interfacial entanglements as determined from Primitive Path Analysis. Bulk polymers fail through craze formation, followed by craze breakdown through chain scission. At small t welded interfaces are not strong enough to support craze formation and fail at small strains through chain pullout at the interface. Once chains have formed an average of about one entanglement across the interface, a stable crazemore » is formed throughout the sample. The failure stress of the craze rises with welding time and the mode of craze breakdown changes from chain pullout to chain scission as the interface approaches bulk strength. The interfacial fracture energy G I is calculated by coupling the simulation results to a continuum fracture mechanics model. As in experiment, G I increases as t 1/2 before saturating at the average bulk fracture energy G b. As in previous studies of shear strength, saturation coincides with the recovery of the bulk entanglement density. Before saturation, G I is proportional to the areal density of interfacial entanglements. Immiscibiltiy limits interdiffusion and thus suppresses entanglements at the interface. Even small degrees of immisciblity reduce interfacial entanglements enough that failure occurs by chain pullout and G I << G b.« less

Electronic and molecular structure of carbon grains

NASA Technical Reports Server (NTRS)

Almloef, Jan; Luethi, Hans-Peter

1990-01-01

Clusters of carbon atoms have been studied with large-scale ab initio calculations. Planar, single-sheet graphite fragments with 6 to 54 atoms were investigated, as well as the spherical C(sub 60) Buckminsterfullerene molecule. Polycyclic aromatic hydrocarbons (PAHs) have also been considered. Thermodynamic differences between diamond- and graphite-like grains have been studied in particular. Saturation of the peripheral bonds with hydrogen is found to provide a smooth and uniform convergence of the properties with increasing cluster size. For the graphite-like clusters the convergence to bulk values is much slower than for the three-dimensional complexes.

Phosphorus ionization in silicon doped by self-assembled macromolecular monolayers

NASA Astrophysics Data System (ADS)

Wu, Haigang; Li, Ke; Gao, Xuejiao; Dan, Yaping

2017-10-01

Individual dopant atoms can be potentially controlled at large scale by the self-assembly of macromolecular dopant carriers. However, low concentration phosphorus dopants often suffer from a low ionization rate due to defects and impurities introduced by the carrier molecules. In this work, we demonstrated a nitrogen-free macromolecule doping technique and investigated the phosphorus ionization process by low temperature Hall effect measurements. It was found that the phosphorus dopants diffused into the silicon bulk are in nearly full ionization. However, the electrons ionized from the phosphorus dopants are mostly trapped by deep level defects that are likely carbon interstitials.

A practical large scale/high speed data distribution system using 8 mm libraries

NASA Technical Reports Server (NTRS)

Howard, Kevin

1993-01-01

Eight mm tape libraries are known primarily for their small size, large storage capacity, and low cost. However, many applications require an additional attribute which, heretofore, has been lacking -- high transfer rate. Transfer rate is particularly important in a large scale data distribution environment -- an environment in which 8 mm tape should play a very important role. Data distribution is a natural application for 8 mm for several reasons: most large laboratories have access to 8 mm tape drives, 8 mm tapes are upwardly compatible, 8 mm media are very inexpensive, 8 mm media are light weight (important for shipping purposes), and 8 mm media densely pack data (5 gigabytes now and 15 gigabytes on the horizon). If the transfer rate issue were resolved, 8 mm could offer a good solution to the data distribution problem. To that end Exabyte has analyzed four ways to increase its transfer rate: native drive transfer rate increases, data compression at the drive level, tape striping, and homogeneous drive utilization. Exabyte is actively pursuing native drive transfer rate increases and drive level data compression. However, for non-transmitted bulk data applications (which include data distribution) the other two methods (tape striping and homogeneous drive utilization) hold promise.

Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Runguang; Xie, Qingge; Wang, Yan-Dong

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial-temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (μXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem μXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands.more » Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through μXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials.« less

Heat transfer to and from vegetated surfaces - An analytical method for the bulk exchange coefficients

NASA Technical Reports Server (NTRS)

Massman, William J.

1987-01-01

The semianalytical model outlined in a previous study (Massman, 1987) to describe momentum exchange between the atmosphere and vegetated surfaces is extended to include the exchange of heat. The methods employed are based on one-dimensional turbulent diffusivities, and use analytical solutions to the steady-state diffusion equation. The model is used to assess the influence that the canopy foliage structure and density, the wind profile structure within the canopy, and the shelter factor can have upon the inverse surface Stanton number (kB exp -1), as well as to explore the consequences of introducing a scalar displacement height which can be different from the momentum displacement height. In general, the triangular foliage area density function gives results which agree more closely with observations than that for constant foliage area density. The intended application of this work is for parameterizing the bulk aerodynamic resistances for heat and momentum exchange for use within large-scale models of plant-atmosphere exchanges.

Coatable Li4 SnS4 Solid Electrolytes Prepared from Aqueous Solutions for All-Solid-State Lithium-Ion Batteries.

PubMed

Choi, Young Eun; Park, Kern Ho; Kim, Dong Hyeon; Oh, Dae Yang; Kwak, Hi Ram; Lee, Young-Gi; Jung, Yoon Seok

2017-06-22

Bulk-type all-solid-state lithium-ion batteries (ASLBs) for large-scale energy-storage applications have emerged as a promising alternative to conventional lithium-ion batteries (LIBs) owing to their superior safety. However, the electrochemical performance of bulk-type ASLBs is critically limited by the low ionic conductivity of solid electrolytes (SEs) and poor ionic contact between the active materials and SEs. Herein, highly conductive (0.14 mS cm -1 ) and dry-air-stable SEs (Li 4 SnS 4 ) are reported, which are prepared using a scalable aqueous-solution process. An active material (LiCoO 2 ) coated by solidified Li 4 SnS 4 from aqueous solutions results in a significant improvement in the electrochemical performance of ASLBs. Side-effects of the exposure of LiCoO 2 to aqueous solutions are minimized by using predissolved Li 4 SnS 4 solution. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

DOE PAGES

Li, Runguang; Xie, Qingge; Wang, Yan-Dong; ...

2017-12-28

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial-temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (μXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem μXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands.more » Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through μXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials.« less

On the solvation of the phosphocholine headgroup in an aqueous propylene glycol solution

NASA Astrophysics Data System (ADS)

Rhys, Natasha H.; Al-Badri, Mohamed Ali; Ziolek, Robert M.; Gillams, Richard J.; Collins, Louise E.; Lawrence, M. Jayne; Lorenz, Christian D.; McLain, Sylvia E.

2018-04-01

The atomic-scale structure of the phosphocholine (PC) headgroup in 30 mol. % propylene glycol (PG) in an aqueous solution has been investigated using a combination of neutron diffraction with isotopic substitution experiments and computer simulation techniques—molecular dynamics and empirical potential structure refinement. Here, the hydration of the PC headgroup remains largely intact compared with the hydration of this group in a bilayer and in a bulk water solution, with the PG molecules showing limited interactions with the headgroup. When direct PG interactions with PC do occur, they are most likely to coordinate to the 3+N (CH 3 ) motifs. Further, PG does not affect the bulk water structure and the addition of PC does not perturb the PG-solvent interactions. This suggests that the reason why PG is able to penetrate into membranes easily is that it does not form strong-hydrogen bonding or electrostatic interactions with the headgroup allowing it to easily move across the membrane barrier.

Direct evidence for the spin cycloid in strained nanoscale bismuth ferrite thin films

PubMed Central

Bertinshaw, Joel; Maran, Ronald; Callori, Sara J.; Ramesh, Vidya; Cheung, Jeffery; Danilkin, Sergey A.; Lee, Wai Tung; Hu, Songbai; Seidel, Jan; Valanoor, Nagarajan; Ulrich, Clemens

2016-01-01

Magnonic devices that utilize electric control of spin waves mediated by complex spin textures are an emerging direction in spintronics research. Room-temperature multiferroic materials, such as bismuth ferrite (BiFeO3), would be ideal candidates for this purpose. To realize magnonic devices, a robust long-range spin cycloid with well-known direction is desired, since it is a prerequisite for the magnetoelectric coupling. Despite extensive investigation, the stabilization of a large-scale uniform spin cycloid in nanoscale (100 nm) thin BiFeO3 films has not been accomplished. Here, we demonstrate cycloidal spin order in 100 nm BiFeO3 thin films through the careful choice of crystallographic orientation, and control of the electrostatic and strain boundary conditions. Neutron diffraction, in conjunction with X-ray diffraction, reveals an incommensurate spin cycloid with a unique [11] propagation direction. While this direction is different from bulk BiFeO3, the cycloid length and Néel temperature remain equivalent to bulk at room temperature. PMID:27585637

Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

PubMed Central

Li, Runguang; Xie, Qingge; Wang, Yan-Dong; Liu, Wenjun; Wang, Mingguang; Wu, Guilin; Li, Xiaowu; Zhang, Minghe; Lu, Zhaoping; Geng, Chang; Zhu, Ting

2018-01-01

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial−temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (μXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem μXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands. Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through μXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials. PMID:29284751

Evidence of long-term seasonal climate forcing in rhizolith isotopes during the last glaciation

USGS Publications Warehouse

Wang, Hongfang; Ambrose, S.H.; Fouke, B.W.

2004-01-01

High density carbonate rhizoliths were found from a loess-paleosol succession from the late Wisconsin period (21-11 ka) in Illinois. Their morphology shows that they formed in a close contact with living and decomposing roots, suggesting a root/microbial respiration origin. Carbon (??13C) and oxygen (??18O) isotopic analyses were performed on 36 and 37 individual rhizoliths of two separate 10 cm intervals and 98 bulk rhizoliths of all 10 cm intervals. The results of the individual rhizolith ??13C and ??18O analyses suggest that the carbon source was largely derived from respiring C3, C4 and microbial biomass, and that meteoric water was controlled mainly by warm-season precipitation. The results of bulk rhizolith ??13C and ??18O analyses show that warm-season proxies varied in phase with glacial fluctuations at submillennial scales, suggesting long-term seasonal forcing may have played an important role on climate change during the late Wisconsin glaciation in North America. Copyright 2004 by the American Geophysical Union.

Steps Towards Understanding Large-scale Deformation of Gas Hydrate-bearing Sediments

NASA Astrophysics Data System (ADS)

Gupta, S.; Deusner, C.; Haeckel, M.; Kossel, E.

2016-12-01

Marine sediments bearing gas hydrates are typically characterized by heterogeneity in the gas hydrate distribution and anisotropy in the sediment-gas hydrate fabric properties. Gas hydrates also contribute to the strength and stiffness of the marine sediment, and any disturbance in the thermodynamic stability of the gas hydrates is likely to affect the geomechanical stability of the sediment. Understanding mechanisms and triggers of large-strain deformation and failure of marine gas hydrate-bearing sediments is an area of extensive research, particularly in the context of marine slope-stability and industrial gas production. The ultimate objective is to predict severe deformation events such as regional-scale slope failure or excessive sand production by using numerical simulation tools. The development of such tools essentially requires a careful analysis of thermo-hydro-chemo-mechanical behavior of gas hydrate-bearing sediments at lab-scale, and its stepwise integration into reservoir-scale simulators through definition of effective variables, use of suitable constitutive relations, and application of scaling laws. One of the focus areas of our research is to understand the bulk coupled behavior of marine gas hydrate systems with contributions from micro-scale characteristics, transport-reaction dynamics, and structural heterogeneity through experimental flow-through studies using high-pressure triaxial test systems and advanced tomographical tools (CT, ERT, MRI). We combine these studies to develop mathematical model and numerical simulation tools which could be used to predict the coupled hydro-geomechanical behavior of marine gas hydrate reservoirs in a large-strain framework. Here we will present some of our recent results from closely co-ordinated experimental and numerical simulation studies with an objective to capture the large-deformation behavior relevant to different gas production scenarios. We will also report on a variety of mechanically relevant test scenarios focusing on effects of dynamic changes in gas hydrate saturation, highly uneven gas hydrate distributions, focused fluid migration and gas hydrate production through depressurization and CO2 injection.

Artificial fluid properties for large-eddy simulation of compressible turbulent mixing

NASA Astrophysics Data System (ADS)

Cook, Andrew W.

2007-05-01

An alternative methodology is described for large-eddy simulation (LES) of flows involving shocks, turbulence, and mixing. In lieu of filtering the governing equations, it is postulated that the large-scale behavior of a LES fluid, i.e., a fluid with artificial properties, will be similar to that of a real fluid, provided the artificial properties obey certain constraints. The artificial properties consist of modifications to the shear viscosity, bulk viscosity, thermal conductivity, and species diffusivity of a fluid. The modified transport coefficients are designed to damp out high wavenumber modes, close to the resolution limit, without corrupting lower modes. Requisite behavior of the artificial properties is discussed and results are shown for a variety of test problems, each designed to exercise different aspects of the models. When combined with a tenth-order compact scheme, the overall method exhibits excellent resolution characteristics for turbulent mixing, while capturing shocks and material interfaces in a crisp fashion.

A three-scale model for ionic solute transport in swelling clays incorporating ion-ion correlation effects

NASA Astrophysics Data System (ADS)

Le, Tien Dung; Moyne, Christian; Murad, Marcio A.

2015-01-01

A new three-scale model is proposed to describe the movement of ionic species of different valences in swelling clays characterized by three separate length scales (nano, micro, and macro) and two levels of porosity (nano- and micropores). At the finest (nano) scale the medium is treated as charged clay particles saturated by aqueous electrolyte solution containing monovalent and divalent ions forming the electrical double layer. A new constitutive law is constructed for the disjoining pressure based on the numerical resolution of non-local problem at the nanoscale which, in contrast to the Poisson-Boltzmann theory for point charge ions, is capable of capturing the short-range interactions between the ions due to their finite size. At the intermediate scale (microscale), the two-phase homogenized particle/electrolyte solution system is represented by swollen clay clusters (or aggregates) with the nanoscale disjoining pressure incorporated in a modified form of Terzaghi's effective principle. At the macroscale, the electro-chemical-mechanical couplings within clay clusters is homogenized with the ion transport in the bulk fluid lying in the micro pores. The resultant macroscopic picture is governed by a three-scale model wherein ion transport takes place in the bulk solution strongly coupled with the mechanics of the clay clusters which play the role of sources/sinks of mass to the bulk fluid associated with ion adsorption/desorption in the electrical double layer at the nanoscale. Within the context of the quasi-steady version of the multiscale model, wherein the electrolyte solution in the nanopores is assumed at instantaneous thermodynamic equilibrium with the bulk fluid in the micropores, we build-up numerically the ion-adsorption isotherms along with the constitutive law of the retardation coefficients of monovalent and divalent ions. In addition, the constitutive law for the macroscopic swelling pressure is reconstructed numerically showing patterns of attractive forces between particles for bivalent ions for particular ranges of bulk concentrations. The three-scale model is applied to numerically simulate ion diffusion in a compacted clay liner underneath a sanitary landfill. Owing to the distinct constitutive behavior of the swelling pressure and partition coefficient for each ionic species, different compaction regimes and diffusion/adsorption patterns, with totally different characteristic time scales, are observed for sodium and calcium migration in the clay liner.

Uncovering a facile large-scale synthesis of LiNi1/3Co1/3Mn1/3O2 nanoflowers for high power lithium-ion batteries

NASA Astrophysics Data System (ADS)

Hua, Wei-Bo; Guo, Xiao-Dong; Zheng, Zhuo; Wang, Yan-Jie; Zhong, Ben-He; Fang, Baizeng; Wang, Jia-Zhao; Chou, Shu-Lei; Liu, Heng

2015-02-01

Developing advanced electrode materials that deliver high energy at ultra-fast charge and discharge rates are very crucial to meet an increasing large-scale market demand for high power lithium ion batteries (LIBs). A three-dimensional (3D) nanoflower structure is successfully developed in the large-scale synthesis of LiNi1/3Co1/3Mn1/3O2 material for the first time. The fast co-precipitation is the key technique to prepare the nanoflower structure in our method. After heat treatment, the obtained LiNi1/3Co1/3Mn1/3O2 nanoflowers (NL333) pronouncedly present a pristine flower-like nano-architecture and provide fast pathways for the transport of Li-ions and electrons. As a cathode material in a LIB, the prepared NL333 electrode demonstrates an outstanding high-rate capability. Particularly, in a narrow voltage range of 2.7-4.3 V, the discharge capacity at an ultra-fast charge-discharge rate (20C) is up to 126 mAh g-1, which reaches 78% of that at 0.2C, and is much higher than that (i.e., 44.17%) of the traditional bulk LiNi1/3Co1/3Mn1/3O2.

Physiological effects of pH gradients on Escherichia coli during plasmid DNA production.

PubMed

Cortés, José T; Flores, Noemí; Bolívar, Francisco; Lara, Alvaro R; Ramírez, Octavio T

2016-03-01

A two-compartment scale-down system was used to mimic pH heterogeneities that can occur in large-scale bioreactors. The system consisted of two interconnected stirred tank reactors (STRs) where one of them represented the conditions of the bulk of the fluid and the second one the zone of alkali addition for pH control. The working volumes ratio of the STRs was set to 20:1 in order to simulate the relative sizes of the bulk and alkali addition zones, respectively, in large-scale bioreactors. Residence times (tR ) in the alkali addition STR of 60, 120, 180, and 240 s were simulated during batch cultures of an engineered Escherichia coli strain that produced plasmid DNA (pDNA). pH gradients of up to 0.9 units, between the two compartments, were attained. The kinetic, stoichiometric, and pDNA topological changes due to the pH gradients were studied and compared to cultures at constant pH of 7.2 and 8.0. As the tR increased, the pDNA and biomass yields, as well as pDNA final titer decreased, whereas the accumulation of organic acids increased. Furthermore, the transcriptional response of 10 selected genes to alkaline stress (pH 8.0) and pH gradients was monitored at different stages of the cultures. The selected genes coded for ion transporters, amino acids catabolism enzymes, and transcriptional regulators. The transcriptional response of genes coding for amino acids catabolism, in terms of relative transcription level and stage of maximal expression, was different when the alkaline stress was constant or transient. This suggests the activation of different mechanisms by E. coli to cope with pH fluctuations compared to constant alkaline pH. Moreover, the transcriptional response of genes related to negative control of DNA synthesis did not correlate with the lower pDNA yields. This is the first study that reports the effects of pH gradients on pDNA production by E. coli cultures. The information presented can be useful for the design of better bioreactor scale-up strategies. © 2015 Wiley Periodicals, Inc.

Uneven flows: On cosmic bulk flows, local observers, and gravity

NASA Astrophysics Data System (ADS)

Hellwing, Wojciech A.; Bilicki, Maciej; Libeskind, Noam I.

2018-05-01

Using N -body simulations we study the impact of various systematic effects on the low-order moments of the cosmic velocity field: the bulk flow (BF) and the cosmic Mach number (CMN). We consider two types of systematics: those related to survey properties and those induced by the observer's location in the Universe. In the former category we model sparse sampling, velocity errors, and survey incompleteness (radial and geometrical). In the latter, we consider local group (LG) analogue observers, placed in a specific location within the cosmic web, satisfying various observational criteria. We differentiate such LG observers from Copernican ones, who are at random locations. We report strong systematic effects on the measured BF and CMN induced by sparse sampling, velocity errors and radial incompleteness. For BF most of these effects exceed 10% for scales R ≲100 h-1 Mpc . For CMN some of these systematics can be catastrophically large (i.e., >50 %) also on bigger scales. Moreover, we find that the position of the observer in the cosmic web significantly affects the locally measured BF (CMN), with effects as large as ˜20 % (30 % ) at R ≲50 h-1 Mpc for a LG-like observer as compared to a random one. This effect is comparable to the sample variance at the same scales. Such location-dependent effects have not been considered previously in BF and CMN studies and here we report their magnitude and scale for the first time. To highlight the importance of these systematics, we additionally study a model of modified gravity with ˜15 % enhanced growth rate (compared to general relativity). We found that the systematic effects can mimic the modified gravity signal. The worst-case scenario is realized for a case of a LG-like observer, when the effects induced by local structures are degenerate with the enhanced growth rate fostered by modified gravity. Our results indicate that dedicated constrained simulations and realistic mock galaxy catalogs will be absolutely necessary to fully benefit from the statistical power of the forthcoming peculiar velocity data from surveys such as TAIPAN, WALLABY, COSMICFLOWS-4 and SKA.

Seismic peak amplitude as a predictor of TOC content in shallow marine sediments

NASA Astrophysics Data System (ADS)

Neto, Arthur Ayres; Mota, Bruno Bourguignon; Belem, André Luiz; Albuquerque, Ana Luiza; Capilla, Ramsés

2016-10-01

Acoustic remote sensing is a highly effective tool for exploring the seafloor of both deep and shallow marine settings. Indeed, the acoustic response depends on several physicochemical factors such as sediment grain size, bulk density, water content, and mineralogy. The objective of the present study is to assess the suitability of seismic peak amplitude as a predictor of total organic carbon (TOC) content in shallow marine sediments, based on data collected in the Cabo Frio mud belt in an upwelling zone off southeastern Brazil. These comprise records of P-wave velocity ( V P) along 680 km of high-resolution single-channel seismic surveys, combined with analyses of grain size, wet bulk density, absolute water content and TOC content for four piston-cores. TOC contents of sediments from 13 box-cores served to validate the methodology. The results show well-defined positive correlations between TOC content and mean grain size (phi scale) as well as absolute water content, and negative correlations with V P, wet bulk density, and acoustic impedance. These relationships yield a regression equation by which TOC content can be satisfactorily predicted on the basis of acoustic impedance for this region: y = - 4.84 ln( x) + 40.04. Indeed, the derived TOC contents differ by only 5% from those determined by geochemical analysis. After appropriate calibration, acoustic impedance can thus be conveniently used as a predictor of large-scale spatial distributions of organic carbon enrichment in marine sediments. This not only contributes to optimizing scientific project objectives, but also enhances the cost-effectiveness of marine surveys by greatly reducing the ship time commonly required for grid sampling.

The Casimir effect in rugby-ball type flux compactifications

NASA Astrophysics Data System (ADS)

Minamitsuji, M.

2008-04-01

We discuss volume stabilization in a 6D braneworld model based on 6D supergravity theory. The internal space is compactified by magnetic flux and contains codimension two 3-branes (conical singularities) as its boundaries. In general the external 4D spacetime is warped and in the unwrapped limit the shape of the internal space looks like a 'rugby ball'. The size of the internal space is not fixed due to the scale invariance of the supergravity theory. We discuss the possibility of volume stabilization by the Casimir effect for a massless, minimally coupled bulk scalar field. The main obstacle in studying this case is that the brane (conical) part of the relevant heat kernel coefficient (a6) has not been formulated. Thus as a first step, we consider the 4D analog model with boundary codimension two 1-branes. The spacetime structure of the 4D model is very similar to that of the original 6D model, where now the relevant heat kernel coefficient is well known. We derive the one-loop effective potential induced by a scalar field in the bulk by employing zeta function regularization with heat kernel analysis. As a result, the volume is stabilized for most possible choices of the parameters. Especially, for a larger degree of warping, our results imply that a large hierarchy between the mass scales and a tiny amount of effective cosmological constant can be realized on the brane. In the non-warped limit the ratio tends to converge to the same value, independently of the bulk gauge coupling constant. Finally, we will analyze volume stabilization in the original model 6D by employing the same mode-sum technique.

Spectroscopic diagnostics of extended corona and solar wind with UVCS/Spartan

NASA Technical Reports Server (NTRS)

Strachan, L.; Gardner, L. D.; Kohl, J. L.

1995-01-01

The primary goal of the Ultraviolet Coronal Spectrometer on Spartan 201 (UVCS/Spartan) is to make spectroscopic diagnostic measurements that can be used to derive plasma parameters in the extended solar corona where it is believed that significant heating of the corona and acceleration of the solar wind take place. Direct and indirect measurements of particle velocity distribution, thermal and non-thermal temperatures, and bulk outflow velocities are crucial to aid in the identification of physical processes that may be responsible for coronal heating and solar wind acceleration. UVCS/Spartan has made two flights in April 1993 and September 1994, the latter coinciding with the South Polar Passage of the Ulysses spacecraft. Observations were made of the large-scale structures and sub-structures of coronal holes and streamers at heliocentric heights between 1.5 solar radii and 3.5 solar radii. Measurements were made of H I Lyman-alpha intensities and profiles, and line intensities of minor ions like O(5+) and Fe(11+). We will present results from the flights and discuss how these measurements are used to constrain values for the proton thermal and non-thermal kinetic temperatures, proton bulk outflow velocities, and minor ion temperatures and bulk outflow velocities. Plans for the upcoming flight in July 1995 will also be discussed.

Nitric Oxide PLIF Measurements in the Hypersonic Materials Environmental Test System (HYMETS)

NASA Technical Reports Server (NTRS)

Inman, Jennifer A.; Bathel, Brett F.; Johansen, Craig T.; Danehy, Paul M.; Jones, Stephen B.; Gragg, Jeffrey G.; Splinter, Scott C.; McRae, Colin D.

2013-01-01

Planar laser-induced fluorescence (PLIF) of naturally occurring nitric oxide (NO) has been used to obtain instantaneous flow visualization images, and to make both radial and axial velocity measurements in the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. This represents the first application of NO PLIF flow visualization in HYMETS. Results are presented at selected facility run conditions, including some in a simulated Earth atmosphere (75% nitrogen, 20% oxygen, 5% argon) and others in a simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon), for specific bulk enthalpies ranging from 6.5 MJ/kg to 18.4 MJ/kg. Flow visualization images reveal the presence of large scale unsteady flow structures, and indicate nitric oxide fluorescence signal over more than 70% of the core flow for specific bulk enthalpies below about 11 MJ/kg, but over less than 10% of the core flow for specific bulk enthalpies above about 16 MJ/kg. Axial velocimetry was performed using molecular tagging velocimetry (MTV). Axial velocities of about 3 km/s were measured along the centerline. Radial velocimetry was performed by scanning the wavelength of the narrowband laser and analyzing the resulting Doppler shift. Radial velocities of +/- 0.5 km/s were measured.

Porosity and Permeability of Chondritic Materials

NASA Technical Reports Server (NTRS)

Zolensky, Michael E.; Corrigan, Catherine M.; Dahl, Jason; Long, Michael

1996-01-01

We have investigated the porosity of a large number of chondritic interplanetary dust particles and meteorites by three techniques: standard liquid/gas flow techniques, a new, non-invasive ultrasonic technique, and image processing of backscattered images . The latter technique is obviously best suited to sub-kg sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquid/gas flow techniques, and a new, non-destructive pressure release technique. We find that chondritic IDP's have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. These values suggest IDP bulk densities of 1.1 to 3.3 g/cc. Type 1-3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1-3 chondrites have the same approximate range as exhibited by matrix, indicating that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as matrix. These results reveal that the porosity of primitive materials at scales ranging from nanogram to kilogram are similar, implying similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, or chondrite type.

Nitric Oxide PLIF Measurements in the Hypersonic Materials Environmental Test System (HYMETS)

NASA Technical Reports Server (NTRS)

Inman, Jennifer A.; Bathel, Brett F.; Johansen, Craig T.; Danehy, Paul M.; Jones, Stephen B.; Gragg, Jeffrey G.; Splinter, Scott C.

2011-01-01

A nonintrusive laser-based measurement system has been applied for the first time in the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. Planar laser-induced fluorescence of naturally occurring nitric oxide (NO) has been used to obtain instantaneous flow visualization images, and to make both radial and axial velocity measurements. Results are presented at selected facility run conditions, including some in simulated Earth atmosphere (75% nitrogen, 20% oxygen, 5% argon) and others in simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon), for bulk enthalpies ranging from 6.5 MJ/kg to 18.4 MJ/kg. Flow visualization images reveal the presence of large scale unsteady flow structures, and indicate nitric oxide fluorescence signal over more than 70% of the core flow for bulk enthalpies below about 11 MJ/kg, but over less than 10% of the core flow for bulk enthalpies above about 16 MJ/kg. Axial velocimetry was performed using molecular tagging velocimetry (MTV). Axial velocities of about 3 km/s were measured along the centerline. Radial velocimetry was performed by scanning the wavelength of the narrowband laser and analyzing the resulting Doppler shift. Radial velocities of 0.5km/s were measured.

Holographic signatures of cosmological singularities.

PubMed

Engelhardt, Netta; Hertog, Thomas; Horowitz, Gary T

2014-09-19

To gain insight into the quantum nature of cosmological singularities, we study anisotropic Kasner solutions in gauge-gravity duality. The dual description of the bulk evolution towards the singularity involves N=4 super Yang-Mills theory on the expanding branch of deformed de Sitter space and is well defined. We compute two-point correlators of Yang-Mills operators of large dimensions using spacelike geodesics anchored on the boundary. The correlators show a strong signature of the singularity around horizon scales and decay at large boundary separation at different rates in different directions. More generally, the boundary evolution exhibits a process of particle creation similar to that in inflation. This leads us to conjecture that information on the quantum nature of cosmological singularities is encoded in long-wavelength features of the boundary wave function.

Holography and the Coleman-Mermin-Wagner theorem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anninos, Dionysios; Hartnoll, Sean A.; Iqbal, Nabil

2010-09-15

In 2+1 dimensions at finite temperature, spontaneous symmetry breaking of global symmetries is precluded by large thermal fluctuations of the order parameter. The holographic correspondence implies that analogous effects must also occur in 3+1 dimensional theories with gauged symmetries in certain curved spacetimes with horizon. By performing a one loop computation in the background of a holographic superconductor, we show that bulk quantum fluctuations wash out the classical order parameter at sufficiently large distance scales. The low temperature phase is seen to exhibit algebraic long-range order. Beyond the specific example we study, holography suggests that IR singular quantum fluctuations ofmore » the fields and geometry will play an interesting role for many 3+1 dimensional asymptotically anti-de Sitter spacetimes with planar horizon.« less

Rare-earth abundances in chondritic meteorites

NASA Technical Reports Server (NTRS)

Evensen, N. M.; Hamilton, P. J.; Onions, R. K.

1978-01-01

Fifteen chondrites, including eight carbonaceous chondrites, were analyzed for rare earth element abundances by isotope dilution. Examination of REE for a large number of individual chondrites shows that only a small proportion of the analyses have flat unfractionated REE patterns within experimental error. While some of the remaining analyses are consistent with magmatic fractionation, many patterns, in particular those with positive Ce anomalies, can not be explained by known magmatic processes. Elemental abundance anomalies are found in all major chondrite classes. The persistence of anomalies in chondritic materials relatively removed from direct condensational processes implies that anomalous components are resistant to equilibrium or were introduced at a late stage of chondrite formation. Large-scale segregation of gas and condensate is implied, and bulk variations in REE abundances between planetary bodies is possible.

Spatial and temporal distribution of pore gas concentrations during mainstream large-scale trough composting in China.

PubMed

Zeng, Jianfei; Shen, Xiuli; Sun, Xiaoxi; Liu, Ning; Han, Lujia; Huang, Guangqun

2018-05-01

With the advantages of high treatment capacity and low operational cost, large-scale trough composting has become one of the mainstream composting patterns in composting plants in China. This study measured concentrations of O 2 , CO 2 , CH 4 and NH 3 on-site to investigate the spatial and temporal distribution of pore gas concentrations during mainstream large-scale trough composting in China. The results showed that the temperature in the center of the pile was obviously higher than that in the side of the pile. Pore O 2 concentration rapidly decreased and maintained <5% (in volume) for 38 days or more in both the center and side of the pile and effective O 2 diffusion occurred at most in every two contiguous layers. Pore CO 2 and CH 4 concentrations at each measurement point were positively correlated (0.436 ≤ r ≤ 0.570, P < 0.01) and the concentrations in the side of the pile were obviously lower than those in the center. The top layer exhibited highest pore O 2 concentration and lowest CO 2 and CH 4 concentrations, and the bottom layer was on the contrary. No significant differences in pore NH 3 concentrations between different layers or between different measurement points in the same layer were found. Therefore, mixing the center and the side of the pile when mechanical turning and adjusting the height of the pile according to the physical properties of bulking agents are suggested to optimize the oxygen distribution and promote the composting process during large-scale trough composting when the pile was naturally aerated, which will contribute to improving the current undesirable atmosphere environment in China. Copyright © 2018 Elsevier Ltd. All rights reserved.

Two fluid anisotropic dark energy models in a scale invariant theory

NASA Astrophysics Data System (ADS)

Tripathy, S. K.; Mishra, B.; Sahoo, P. K.

2017-09-01

Some anisotropic Bianchi V dark energy models are investigated in a scale invariant theory of gravity. We consider two non-interacting fluids such as dark energy and a bulk viscous fluid. Dark energy pressure is considered to be anisotropic in different spatial directions. A dynamically evolving pressure anisotropy is obtained from the models. The models favour phantom behaviour. It is observed that, in presence of dark energy, bulk viscosity has no appreciable effect on the cosmic dynamics.

Ultralight, scalable nano-architected metamaterials (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zheng, Xiaoyu R.

2017-04-01

It has been a long research and engineering pursuit to create lightweight and mechanically robust and energy efficient materials with interconnected porosity. These cellular materials are desirable for a broad range of applications including structural components, lightweight transportation, heat exchange, catalyst supports, battery electrodes and biomaterials. However, the required outstanding properties have remained elusive on lightweight materials (<10kg/m3), constrained by the inherent coupling of material properties and the lack of suitable processes to generate these artificial materials. For example, graphene aerogels have among the lowest record densities 1kg/m^3, but their strength have been degraded to tens to hundreds of Pascal (<10^-8 of that of carbon nanotubes). The attainment of low density has come with a price -- significant reduction of bulk scale properties. We present the design, manufacturing and defect tolerance study of a new class of ultralight, three-dimensional multi-functional architected materials. These 3D bulk metamaterials (polymer, metal, ceramic and combinations thereof) possess weight density comparable to that of carbon aerogel, but with over 10^4 higher stiffness and strength. By designing and studying their hierarchical architectures, material compositions and feature sizes spanning multiple length-scales, we create a wide range of decoupled material properties such as programmable stiffness, tunable strength and fracture toughness as well as programmable possion ratio. With the possibility of incorporating precise control of topological architectures across length-scale sets as well as prediction and optimization of their defect tolerance, we enter into a paradigm where nanoscale material properties can be harnessed and made accessible in large scale objects, opening a wide range of applications of these materials in energy, health care and flexible electronics.

A priori study of subgrid-scale features in turbulent Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Dabbagh, F.; Trias, F. X.; Gorobets, A.; Oliva, A.

2017-10-01

At the crossroad between flow topology analysis and turbulence modeling, a priori studies are a reliable tool to understand the underlying physics of the subgrid-scale (SGS) motions in turbulent flows. In this paper, properties of the SGS features in the framework of a large-eddy simulation are studied for a turbulent Rayleigh-Bénard convection (RBC). To do so, data from direct numerical simulation (DNS) of a turbulent air-filled RBC in a rectangular cavity of aspect ratio unity and π spanwise open-ended distance are used at two Rayleigh numbers R a ∈{1 08,1 010 } [Dabbagh et al., "On the evolution of flow topology in turbulent Rayleigh-Bénard convection," Phys. Fluids 28, 115105 (2016)]. First, DNS at Ra = 108 is used to assess the performance of eddy-viscosity models such as QR, Wall-Adapting Local Eddy-viscosity (WALE), and the recent S3PQR-models proposed by Trias et al. ["Building proper invariants for eddy-viscosity subgrid-scale models," Phys. Fluids 27, 065103 (2015)]. The outcomes imply that the eddy-viscosity modeling smoothes the coarse-grained viscous straining and retrieves fairly well the effect of the kinetic unfiltered scales in order to reproduce the coherent large scales. However, these models fail to approach the exact evolution of the SGS heat flux and are incapable to reproduce well the further dominant rotational enstrophy pertaining to the buoyant production. Afterwards, the key ingredients of eddy-viscosity, νt, and eddy-diffusivity, κt, are calculated a priori and revealed positive prevalent values to maintain a turbulent wind essentially driven by the mean buoyant force at the sidewalls. The topological analysis suggests that the effective turbulent diffusion paradigm and the hypothesis of a constant turbulent Prandtl number are only applicable in the large-scale strain-dominated areas in the bulk. It is shown that the bulk-dominated rotational structures of vortex-stretching (and its synchronous viscous dissipative structures) hold the highest positive values of νt; however, the zones of backscatter energy and counter-gradient heat transport are related to the areas of compressed focal vorticity. More arguments have been attained through a priori investigation of the alignment trends imposed by existing parameterizations for the SGS heat flux, tested here inside RBC. It is shown that the parameterizations based linearly on the resolved thermal gradient are invalid in RBC. Alternatively, the tensor-diffusivity approach becomes a crucial choice of modeling the SGS heat flux, in particular, the tensorial diffusivity that includes the SGS stress tensor. This and other crucial scrutinies on a future modeling to the SGS heat flux in RBC are sought.

High-Efficiency Small Molecule-Based Bulk-Heterojunction Solar Cells Enhanced by Additive Annealing.

PubMed

Li, Lisheng; Xiao, Liangang; Qin, Hongmei; Gao, Ke; Peng, Junbiao; Cao, Yong; Liu, Feng; Russell, Thomas P; Peng, Xiaobin

2015-09-30

Solvent additive processing is important in optimizing an active layer's morphology and thus improving the performance of organic solar cells (OSCs). In this study, we find that how 1,8-diiodooctane (DIO) additive is removed plays a critical role in determining the film morphology of the bulk heterojunction OSCs in inverted structure based on a porphyrin small molecule. Different from the cases reported for polymer-based OSCs in conventional structures, the inverted OSCs upon the quick removal of the additive either by quick vacuuming or methanol washing exhibit poorer performance. In contrast, the devices after keeping the active layers in ambient pressure with additive dwelling for about 1 h (namely, additive annealing) show an enhanced power conversion efficiency up to 7.78% with a large short circuit current of 19.25 mA/cm(2), which are among the best in small molecule-based solar cells. The detailed morphology analyses using UV-vis absorption spectroscopy, grazing incidence X-ray diffraction, resonant soft X-ray scattering, and atomic force microscopy demonstrate that the active layer shows smaller-sized phase separation but improved structure order upon additive annealing. On the contrary, the quick removal of the additive either by quick vacuuming or methanol washing keeps the active layers in an earlier stage of large scaled phase separation.

Comparison of bulk-tank standard plate count and somatic cell count for Wisconsin dairy farms in three size categories.

PubMed

Ingham, S C; Hu, Y; Ané, C

2011-08-01

The objective of this study was to evaluate possible claims by advocates of small-scale dairy farming that milk from smaller Wisconsin farms is of higher quality than milk from larger Wisconsin farms. Reported bulk tank standard plate count (SPC) and somatic cell count (SCC) test results for Wisconsin dairy farms were obtained for February to December, 2008. Farms were sorted into 3 size categories using available size-tracking criteria: small (≤118 cows; 12,866 farms), large (119-713 cattle; 1,565 farms), and confined animal feeding operations (≥714 cattle; 160 farms). Group means were calculated (group=farm size category) for the farms' minimum, median, mean, 90th percentile, and maximum SPC and SCC. Statistical analysis showed that group means for median, mean, 90th percentile, and maximum SPC and SCC were almost always significantly higher for the small farm category than for the large farm and confined animal feeding operations farm categories. With SPC and SCC as quality criteria and the 3 farm size categories of ≤118, 119 to 713, and ≥714 cattle, the claim of Wisconsin smaller farms producing higher quality milk than Wisconsin larger farms cannot be supported. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Nanochannel structures in W enhance radiation tolerance

DOE PAGES

Qin, Wenjing; Ren, Feng; Doerner, Russell P.; ...

2018-04-23

Developing high performance plasma facing materials (PFMs) is one of the greatest challenges for fusion reactors, because PFMs face unprecedented harsh environments including high flux plasma exposure, fast neutron irradiation and large transmutation gas. Tungsten (W) is considered as one of the most promising PFMs. Rapid accumulation of helium (He) atoms in such environments can lead to the He bubbles nucleation and even the formation of nano- to micro-scale “fuzz” on W surface, which greatly degrade the properties of W itself. The possible ejection of large W particulates into the core plasma can cause plasma instabilities. In this paper, wemore » present a new strategy to address the root causes of bubble nucleation and “fuzz” formation by concurrently releasing He outside of W matrix through the nano-engineered channel structure (nanochannels). Comparing to ordinary bulk W, nanochannel W films with high surface-to-volume ratios are found to not only delay the growth of He bubbles, but also suppress the formation of “fuzz” (less than a half of the “fuzz” thickness formation in bulk W). Finally, molecular dynamic (MD) simulation results elucidate that low vacancy formation energy and high He binding energy in the nanochannel surface effectively help He release and affect He clusters distribution in W during He ion irradiation.« less

Nanochannel structures in W enhance radiation tolerance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Wenjing; Ren, Feng; Doerner, Russell P.

Developing high performance plasma facing materials (PFMs) is one of the greatest challenges for fusion reactors, because PFMs face unprecedented harsh environments including high flux plasma exposure, fast neutron irradiation and large transmutation gas. Tungsten (W) is considered as one of the most promising PFMs. Rapid accumulation of helium (He) atoms in such environments can lead to the He bubbles nucleation and even the formation of nano- to micro-scale “fuzz” on W surface, which greatly degrade the properties of W itself. The possible ejection of large W particulates into the core plasma can cause plasma instabilities. In this paper, wemore » present a new strategy to address the root causes of bubble nucleation and “fuzz” formation by concurrently releasing He outside of W matrix through the nano-engineered channel structure (nanochannels). Comparing to ordinary bulk W, nanochannel W films with high surface-to-volume ratios are found to not only delay the growth of He bubbles, but also suppress the formation of “fuzz” (less than a half of the “fuzz” thickness formation in bulk W). Finally, molecular dynamic (MD) simulation results elucidate that low vacancy formation energy and high He binding energy in the nanochannel surface effectively help He release and affect He clusters distribution in W during He ion irradiation.« less

On the Asymptotic Behavior of a Log Gas in the Bulk Scaling Limit in the Presence of a Varying External Potential I

NASA Astrophysics Data System (ADS)

Bothner, Thomas; Deift, Percy; Its, Alexander; Krasovsky, Igor

2015-08-01

We study the determinant , of the integrable Fredholm operator K s acting on the interval (-1, 1) with kernel . This determinant arises in the analysis of a log-gas of interacting particles in the bulk-scaling limit, at inverse temperature , in the presence of an external potential supported on an interval of length . We evaluate, in particular, the double scaling limit of as and , in the region , for any fixed . This problem was first considered by Dyson (Chen Ning Yang: A Great Physicist of the Twentieth Century. International Press, Cambridge, pp. 131-146, 1995).

Engineering Ferroic and Multiferroic Materials for Active Cooling Applications

DTIC Science & Technology

2014-02-11

large strain gradients (>105 m-1) – nearly 5-6 orders of magnitude larger than what can be achieved in bulk-versions of materials. These large strain...larger than what can be achieved in bulk-versions of materials. These large strain gradients gave rise to unexpected crystal and domain structure...parameters that are more favorable for generating a compressively strained variety of the Zr-rich phases. In this case, akin to what has been

[Energy saving achieved by limited filamentous bulking under low dissolved oxygen: derivation, originality and theoretical basis].

PubMed

Peng, Yong-zhen; Guo, Jian-hua; Wang, Shu-ying; Chen, Ying

2008-12-01

How to prevent and control filamentous bulking sludge has being a research focus and attracted much attention. To date despite the extensive research that has been done on bulking sludge, filamentous bulking still occurs world-wide and a comprehensive solution does not seem to be available. Particularly, there are few studies about making use of the characteristics of filamentous bacteria and achieving energy saving by filamentous bulking. Limited filamentous bulking, a novel method for energy saving while equal or better treatment performance by allowing slight and controlled filamentous bulking sludge at low dissolved oxygen (DO), was proposed based on full-scale field observations. The practical operation showed that limited filamentous bulking resulted from a decline in DO concentration. COD, SS and TP removal could be enhanced and energy saving could be achieved by limited filamentous bulking at low DO. The derivation of limited filamentous bulking is introduced firstly, and then the theoretical fundamentals of the technique of limited filamentous bulking are presented and analyzed, including the occurrence of limited filamentous bulking caused by low DO, the enhanced effect of filamentous bacteria on pollutants removal and the energy saving mechanism by using limited filamentous bulking. Besides, the paper provides some new perspectives about the application and research direction of limited filamentous bulking in future.

Gravity-driven dense granular flows

NASA Astrophysics Data System (ADS)

Ertas, Deniz

2002-03-01

Despite their importance in many areas of science and technology, the emergent physics of hard granular systems remain largely obscure, especially when the packing density approaches that of a jammed system. In particular, I will focus on the rheology of gravity-driven dense granular flows on an incline with a ``rough" bottom in two and three dimensions. We have conducted large-scale molecular dynamics simulations of spheres that interact through linear damped spring or Hertzian force laws with a Coulomb failure criterion(D. Ertaş) et al., Europhys. Lett. 56, 214 (2001); L.E. Silbert et al., Phys. Rev. E 64, 051302 (2001).. This flow geometry produces a constant density profile, and reproduces key features of such flows that have been observed experimentally(O. Pouliquen, Phys. Fluids 11), 542 (1999), such as an angle of repose that depends on flow thickness, steady-state solutions at varying heights for a given inclination angle, and the scaling of the mean particle velocity with pile height (< v > ∝ H^3/2). These successes prompted us to carefully examine the rheology in the interior of the pile by measuring the full stress and strain tensors, which are generally unavailable through experiments. The type of force law has little impact on the behavior of the system. The bulk rheology can be approximately described in terms of extensions of Chapman-Enskog theory to dense packings(L. Bocquet et al.), cond-mat/0112072. However, close to the angle of repose, this description fails near the free surface, which exhibits a rheology dominated by normal stress differences that are small in the bulk. This change in rheology can be qualitatively understood in terms of stress-bearing force networks that are continuously formed by ``gravitational inelastic collapse" and destroyed by the imposed strain.

Comparison of landfarming amendments to improve bioremediation of petroleum hydrocarbons in Niger Delta soils.

PubMed

Brown, David M; Okoro, Samson; van Gils, Juami; van Spanning, Rob; Bonte, Matthijs; Hutchings, Tony; Linden, Olof; Egbuche, Uzoamaka; Bruun, Kim Bye; Smith, Jonathan W N

2017-10-15

Large scale landfarming experiments, using an extensive range of treatments, were conducted in the Niger-Delta, Nigeria to study the degradation of oil in contaminated soils. In this work the effect of nutrient addition, biosurfactant, Eisenia fetida (earthworm) enzyme extract, bulking and sorption agents and soil neutralization were tested. It was found that these treatments were successful in removing up to 53% of the total petroleum hydrocarbon in the soil within 16 weeks. A comparison between treatments demonstrated that most were no more effective than agricultural fertilizer addition alone. One strategy that did show better performance was a combination of nutrients, biochar and biosurfactant, which was found to remove 23% more Total Petroleum Hydrocarbons (TPH) than fertilizer alone. However, when performance normalized costs were considered, this treatment became less attractive as a remedial option. Based on this same analysis it was concluded that fertilizer only was the most cost effective treatment. As a consequence, it is recommended that fertilizer is used to enhance the landfarming of hydrocarbon contaminated soils in the Niger Delta. The attenuation rates of both bulk TPH and Total Petroleum Hydrocarbon Criteria Working Group (TPHCWG) fractions are also provided. These values represent one of the first large scale and scientifically tested datasets for treatment of contaminated soil in the Niger Delta region. An inverse correlation between attenuation rates and hydrocarbon molecular weight was observed with heavy fractions showing much slower degradation rates than lighter fractions. Despite this difference, the bioremediation process resulted in significant removal of all TPH compounds independent of carbon number. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Wetting Transition of Nonpolar Neutral Molecule System on a Neutral and Atomic Length Scale Roughness Substrate

NASA Astrophysics Data System (ADS)

Zhou, Shiqi

2018-03-01

One recently proposed new method for accurately determining wetting temperature is applied to the wetting transition occurring in a single component nonpolar neutral molecule system near a neutral planar substrate with roughness produced by cosinusoidal modulation(s). New observations are summarized into five points: (i) for a planar substrate superimposed with one cosinusoidal modulation, with increasing of the periodicity length or the surface attraction force field, or decreasing of the amplitude, wetting temperature T_W drops accordingly and the three parameters show multiplication effect; moreover, both the periodicity length and amplitude effect curves display pole phenomena and saturation phenomena, and the T_W saturation occurs at small (for case of large amplitude) or large (for case of small amplitude) periodicity length side, respectively. (ii) In the case of the planar substrate superimposed with two cosinusoidal modulations with equal periodicity length, the initial phase difference is critical issue that influences the T_W, which decreases with the initial phase difference. (iii) In the case of the planar substrate superimposed with two cosinusoidal modulations with zero phase difference, change of the T_W with one periodicity length under the condition of another periodicity length unchanged is non-monotonous. (iv) When the parameters are chosen such that the T_W draws ever closer to the bulk critical temperature, wetting transition on the roughness substrate eventually does not occur. (v) The present microscopic calculation challenges traditional macroscopic theory by confirming that the atomic length scale roughness always renders the surface less hydrophilic and whereas the mesoscopical roughness renders the surface more hydrophilic. All of these observations summarized can be reasonably explained by the relative strength of the attraction actually enjoyed by the surface gas molecules to the attraction the gas molecules can get when in bulk.

Determining the spatial variability of wetland soil bulk density, organic matter, and the conversion factor between organic matter and organic carbon across coastal Louisiana, U.S.A.

USGS Publications Warehouse

Wang, Hongqing; Piazza, Sarai C.; Sharp, Leigh A.; Stagg, Camille L.; Couvillion, Brady R.; Steyer, Gregory D.; McGinnis, Thomas E.

2016-01-01

Soil bulk density (BD), soil organic matter (SOM) content, and a conversion factor between SOM and soil organic carbon (SOC) are often used in estimating SOC sequestration and storage. Spatial variability in BD, SOM, and the SOM–SOC conversion factor affects the ability to accurately estimate SOC sequestration, storage, and the benefits (e.g., land building area and vertical accretion) associated with wetland restoration efforts, such as marsh creation and sediment diversions. There are, however, only a few studies that have examined large-scale spatial variability in BD, SOM, and SOM–SOC conversion factors in coastal wetlands. In this study, soil cores, distributed across the entire coastal Louisiana (approximately 14,667 km2) were used to examine the regional-scale spatial variability in BD, SOM, and the SOM–SOC conversion factor. Soil cores for BD and SOM analyses were collected during 2006–09 from 331 spatially well-distributed sites in the Coastwide Reference Monitoring System network. Soil cores for the SOM–SOC conversion factor analysis were collected from 15 sites across coastal Louisiana during 2006–07. Results of a split-plot analysis of variance with incomplete block design indicated that BD and SOM varied significantly at a landscape level, defined by both hydrologic basins and vegetation types. Vertically, BD and SOM varied significantly among different vegetation types. The SOM–SOC conversion factor also varied significantly at the landscape level. This study provides critical information for the assessment of the role of coastal wetlands in large regional carbon budgets and the estimation of carbon credits from coastal restoration.

Limit theorems for Lévy walks in d dimensions: rare and bulk fluctuations

NASA Astrophysics Data System (ADS)

Fouxon, Itzhak; Denisov, Sergey; Zaburdaev, Vasily; Barkai, Eli

2017-04-01

We consider super-diffusive Lévy walks in d≥slant 2 dimensions when the duration of a single step, i.e. a ballistic motion performed by a walker, is governed by a power-law tailed distribution of infinite variance and finite mean. We demonstrate that the probability density function (PDF) of the coordinate of the random walker has two different scaling limits at large times. One limit describes the bulk of the PDF. It is the d-dimensional generalization of the one-dimensional Lévy distribution and is the counterpart of the central limit theorem (CLT) for random walks with finite dispersion. In contrast with the one-dimensional Lévy distribution and the CLT this distribution does not have a universal shape. The PDF reflects anisotropy of the single-step statistics however large the time is. The other scaling limit, the so-called ‘infinite density’, describes the tail of the PDF which determines second (dispersion) and higher moments of the PDF. This limit repeats the angular structure of the PDF of velocity in one step. A typical realization of the walk consists of anomalous diffusive motion (described by anisotropic d-dimensional Lévy distribution) interspersed with long ballistic flights (described by infinite density). The long flights are rare but due to them the coordinate increases so much that their contribution determines the dispersion. We illustrate the concept by considering two types of Lévy walks, with isotropic and anisotropic distributions of velocities. Furthermore, we show that for isotropic but otherwise arbitrary velocity distributions the d-dimensional process can be reduced to a one-dimensional Lévy walk. We briefly discuss the consequences of non-universality for the d  >  1 dimensional fractional diffusion equation, in particular the non-uniqueness of the fractional Laplacian.

Dynamics in a Water Interfacial Boundary Layer Investigated with IR Polarization-Selective Pump-Probe Experiments.

PubMed

Yuan, Rongfeng; Yan, Chang; Nishida, Jun; Fayer, Michael D

2017-05-04

The dynamics of water molecules near the surfactant interface in large Aerosol-OT reverse micelles (RMs) (w 0 = 16-25) was investigated with IR polarization-selective pump-probe experiments using the SeCN - anion as a vibrational probe. Linear absorption spectra of RMs (w 0 = 25-2) can be decomposed into the weighted sum of the SeCN - spectra in bulk water and the spectrum of the SeCN - anion interacting with the interfacial sulfonate head groups (w 0 = 1). The spectra of the large RMs, w 0 ≥ 16, are overwhelmingly dominated by the bulk water component. Anisotropy decays (orientational relaxation) of the anion for w 0 ≥ 16 displayed bulk water relaxation (1.4 and 4.5 ps) plus an additional slow decay with a time constant of ∼13 ps. The amplitude of the slow decay was too large to be associated with SeCN - in contact with the interface on the basis of the linear spectrum decomposition. The results indicate that the observed slow components arise from SeCN - in a water boundary layer, in which water molecules are perturbed by the interface but are not directly associated with it. This layer is the transition between water in direct contact with the interface and bulk water in the large RM cores. In the boundary layer, the water dynamics is slow compared to that in bulk water.

Structure of small-scale magnetic fields in the kinematic dynamo theory.

PubMed

Schekochihin, Alexander; Cowley, Steven; Maron, Jason; Malyshkin, Leonid

2002-01-01

A weak fluctuating magnetic field embedded into a a turbulent conducting medium grows exponentially while its characteristic scale decays. In the interstellar medium and protogalactic plasmas, the magnetic Prandtl number is very large, so a broad spectrum of growing magnetic fluctuations is excited at small (subviscous) scales. The condition for the onset of nonlinear back reaction depends on the structure of the field lines. We study the statistical correlations that are set up in the field pattern and show that the magnetic-field lines possess a folding structure, where most of the scale decrease is due to the field variation across itself (rapid transverse direction reversals), while the scale of the field variation along itself stays approximately constant. Specifically, we find that, though both the magnetic energy and the mean-square curvature of the field lines grow exponentially, the field strength and the field-line curvature are anticorrelated, i.e., the curved field is relatively weak, while the growing field is relatively flat. The detailed analysis of the statistics of the curvature shows that it possesses a stationary limiting distribution with the bulk located at the values of curvature comparable to the characteristic wave number of the velocity field and a power tail extending to large values of curvature where it is eventually cut off by the resistive regularization. The regions of large curvature, therefore, occupy only a small fraction of the total volume of the system. Our theoretical results are corroborated by direct numerical simulations. The implication of the folding effect is that the advent of the Lorentz back reaction occurs when the magnetic energy approaches that of the smallest turbulent eddies. Our results also directly apply to the problem of statistical geometry of the material lines in a random flow.

3-D Printing as a Tool to Investigate the Effects of Changes in Rock Microstructures on Permeability

NASA Astrophysics Data System (ADS)

Head, D. A.; Vanorio, T.

2016-12-01

Rocks are naturally heterogeneous; two rock samples with identical bulk properties can vary widely in microstructure. Understanding the evolutionary trends of rock properties requires the ability to connect time-lapse measurements of properties at different scales: the macro- scale used in the laboratory and field analyses capturing the bulk scale changes and the micro- scale used in imaging and digital techniques capturing the changes to the pore space. However, measuring those properties at different scales is very challenging, and sometimes impossible. The advent of modern 3D printing has provided an unprecedented opportunity to link those scales by combining the strengths of digital and experimental rock physics. To determine the feasibility of this technique we characterized the resolution capabilities of two different 3D printers. To calibrate our digital models with our printed models, we created a sample with an analytically solvable permeability. This allowed us to directly compare analytic calculation, numerical simulation, and laboratory measurement of permeability of the exact same sample. Next we took a CT-scanned model of a natural carbonate pore space, then iteratively digitally manipulated, 3D printed, and measured the flow properties in the laboratory. This approach allowed us to access multiple scales digitally and experimentally, to test hypotheses about how changes in rock microstructure due to compaction and dissolution affect bulk transport properties, and to connect laboratory measurements of porosity and permeability to quantities that are traditionally impossible to measure in the laboratory such as changes in surface area and tortuosity. As 3D printing technology continues to advance, we expect this technique to contribute to our ability to characterize the properties of remote and/or delicate samples as well as to test the impact of microstructural alteration on bulk physical properties in the lab in a highly consistent, repeatable manner.

In Situ Observations of PSCs Generated by Gravity Waves

NASA Technical Reports Server (NTRS)

Pfister, Leonhard; Bui, Paul; Mahoney, M. J.; Gandrud, Bruce; Hipskind, K. Stephen (Technical Monitor)

2000-01-01

During SOLVE, the bulk of the in-situ observations of PSCs are of large scale extended structures associated with synoptic scale cooling. The nature of these structures is also determined by layers of high relative NOy that have been stretched into thin layers by advective processes. Some of the in situ observations, however, are clearly correlated with gravity wave signatures. The first goal of this work is to examine these cases and evaluate gravity wave parameters. In particular, we are interested in the intrinsic periods of the waves and their temperature amplitude, which are key ingredients in the nucleation process. Secondly, we will examine some rudimentary properties of the particle size distributions and composition, comparing these with in situ observations of the more extended PSC features. Finally, we will attempt to ascertain the mechanism which generates the gravity waves.

Dark matter and cosmological nucleosynthesis

NASA Technical Reports Server (NTRS)

Schramm, D. N.

1986-01-01

Existing dark matter problems, i.e., dynamics, galaxy formation and inflation, are considered, along with a model which proposes dark baryons as the bulk of missing matter in a fractal universe. It is shown that no combination of dark, nonbaryonic matter can either provide a cosmological density parameter value near unity or, as in the case of high energy neutrinos, allow formation of condensed matter at epochs when quasars already existed. The possibility that correlations among galactic clusters are scale-free is discussed. Such a distribution of matter would yield a fractal of 1.2, close to a one-dimensional universe. Biasing, cosmic superstrings, and percolated explosions and hot dark matter are theoretical approaches that would satisfy the D = 1.2 fractal model of the large-scale structure of the universe and which would also allow sufficient dark matter in halos to close the universe.

Experiences Integrating Transmission and Distribution Simulations for DERs with the Integrated Grid Modeling System (IGMS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmintier, Bryan; Hale, Elaine; Hodge, Bri-Mathias

2016-08-11

This paper discusses the development of, approaches for, experiences with, and some results from a large-scale, high-performance-computer-based (HPC-based) co-simulation of electric power transmission and distribution systems using the Integrated Grid Modeling System (IGMS). IGMS was developed at the National Renewable Energy Laboratory (NREL) as a novel Independent System Operator (ISO)-to-appliance scale electric power system modeling platform that combines off-the-shelf tools to simultaneously model 100s to 1000s of distribution systems in co-simulation with detailed ISO markets, transmission power flows, and AGC-level reserve deployment. Lessons learned from the co-simulation architecture development are shared, along with a case study that explores the reactivemore » power impacts of PV inverter voltage support on the bulk power system.« less

Phthalimide Copolymer Solar Cells

NASA Astrophysics Data System (ADS)

Xin, Hao; Guo, Xugang; Ren, Guoqiang; Kim, Felix; Watson, Mark; Jenekhe, Samson

2010-03-01

Photovoltaic properties of bulk heterojunction solar cells based on phthalimide donor-acceptor copolymers have been investigated. Due to the strong π-π stacking of the polymers, the state-of-the-art thermal annealing approach resulted in micro-scale phase separation and thus negligible photocurrent. To achieve ideal bicontinuous morphology, different strategies including quickly film drying and mixed solvent for film processing have been explored. In these films, nano-sale phase separation was achieved and a power conversion efficiency of 3.0% was obtained. Absorption and space-charge limited current mobility measurements reveal similar light harvesting and hole mobilities in all the films, indicating that the morphology is the dominant factor determining the photovoltaic performance. Our results demonstrate that for highly crystalline and/or low-solubility polymers, finding a way to prevent polymer aggregation and large scale phase separation is critical to realizing high performance solar cells.

Confinement, Desolvation, And Electrosorption Effects on the Diffusion of Ions in Nanoporous Carbon Electrodes

PubMed Central

2015-01-01

Supercapacitors are electrochemical devices which store energy by ion adsorption on the surface of a porous carbon. They are characterized by high power delivery. The use of nanoporous carbon to increase their energy density should not hinder their fast charging. However, the mechanisms for ion transport inside electrified nanopores remain largely unknown. Here we show that the diffusion is characterized by a hierarchy of time scales arising from ion confinement, solvation, and electrosorption effects. By combining electrochemistry experiments with molecular dynamics simulations, we determine the in-pore conductivities and diffusion coefficients and their variations with the applied potential. We show that the diffusion of the ions is slower by 1 order of magnitude compared to the bulk electrolyte. The desolvation of the ions occurs on much faster time scales than electrosorption. PMID:26369420

RACORO continental boundary layer cloud investigations. 2. Large-eddy simulations of cumulus clouds and evaluation with in-situ and ground-based observations

DOE PAGES

Endo, Satoshi; Fridlind, Ann M.; Lin, Wuyin; ...

2015-06-19

A 60-hour case study of continental boundary layer cumulus clouds is examined using two large-eddy simulation (LES) models. The case is based on observations obtained during the RACORO Campaign (Routine Atmospheric Radiation Measurement [ARM] Aerial Facility [AAF] Clouds with Low Optical Water Depths [CLOWD] Optical Radiative Observations) at the ARM Climate Research Facility's Southern Great Plains site. The LES models are driven by continuous large-scale and surface forcings, and are constrained by multi-modal and temporally varying aerosol number size distribution profiles derived from aircraft observations. We compare simulated cloud macrophysical and microphysical properties with ground-based remote sensing and aircraft observations.more » The LES simulations capture the observed transitions of the evolving cumulus-topped boundary layers during the three daytime periods, and generally reproduce variations of droplet number concentration with liquid water content (LWC), corresponding to the gradient between the cloud centers and cloud edges at given heights. The observed LWC values fall within the range of simulated values; the observed droplet number concentrations are commonly higher than simulated, but differences remain on par with potential estimation errors in the aircraft measurements. Sensitivity studies examine the influences of bin microphysics versus bulk microphysics, aerosol advection, supersaturation treatment, and aerosol hygroscopicity. Simulated macrophysical cloud properties are found to be insensitive in this non-precipitating case, but microphysical properties are especially sensitive to bulk microphysics supersaturation treatment and aerosol hygroscopicity.« less

Ab initio calculations for industrial materials engineering: successes and challenges.

PubMed

Wimmer, Erich; Najafabadi, Reza; Young, George A; Ballard, Jake D; Angeliu, Thomas M; Vollmer, James; Chambers, James J; Niimi, Hiroaki; Shaw, Judy B; Freeman, Clive; Christensen, Mikael; Wolf, Walter; Saxe, Paul

2010-09-29

Computational materials science based on ab initio calculations has become an important partner to experiment. This is demonstrated here for the effect of impurities and alloying elements on the strength of a Zr twist grain boundary, the dissociative adsorption and diffusion of iodine on a zirconium surface, the diffusion of oxygen atoms in a Ni twist grain boundary and in bulk Ni, and the dependence of the work function of a TiN-HfO(2) junction on the replacement of N by O atoms. In all of these cases, computations provide atomic-scale understanding as well as quantitative materials property data of value to industrial research and development. There are two key challenges in applying ab initio calculations, namely a higher accuracy in the electronic energy and the efficient exploration of large parts of the configurational space. While progress in these areas is fueled by advances in computer hardware, innovative theoretical concepts combined with systematic large-scale computations will be needed to realize the full potential of ab initio calculations for industrial applications.

Nano-imprint gold grating as refractive index sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumari, Sudha; Mohapatra, Saswat; Moirangthem, Rakesh S.

Large scale of fabrication of plasmonic nanostructures has been a challenging task due to time consuming process and requirement of expensive nanofabrication tools such as electron beam lithography system, focused ion beam system, and extreme UV photolithography system. Here, we present a cost-effective fabrication technique so called soft nanoimprinting to fabricate nanostructures on the larger sample area. In our fabrication process, a commercially available optical DVD disc was used as a template which was imprinted on a polymer glass substrate to prepare 1D polymer nano-grating. A homemade nanoimprinting setup was used in this fabrication process. Further, a label-free refractive indexmore » sensor was developed by utilizing the properties of surface plasmon resonance (SPR) of a gold coated 1D polymer nano-grating. Refractive index sensing was tested by exposing different solutions of glycerol-water mixture on the surface of gold nano-grating. The calculated bulk refractive index sensitivity was found to be 751nm/RIU. We believed that our proposed SPR sensor could be a promising candidate for developing low-cost refractive index sensor with high sensitivity on a large scale.« less

Enhancing Solar Cell Efficiencies through 1-D Nanostructures

PubMed Central

2009-01-01

The current global energy problem can be attributed to insufficient fossil fuel supplies and excessive greenhouse gas emissions resulting from increasing fossil fuel consumption. The huge demand for clean energy potentially can be met by solar-to-electricity conversions. The large-scale use of solar energy is not occurring due to the high cost and inadequate efficiencies of existing solar cells. Nanostructured materials have offered new opportunities to design more efficient solar cells, particularly one-dimensional (1-D) nanomaterials for enhancing solar cell efficiencies. These 1-D nanostructures, including nanotubes, nanowires, and nanorods, offer significant opportunities to improve efficiencies of solar cells by facilitating photon absorption, electron transport, and electron collection; however, tremendous challenges must be conquered before the large-scale commercialization of such cells. This review specifically focuses on the use of 1-D nanostructures for enhancing solar cell efficiencies. Other nanostructured solar cells or solar cells based on bulk materials are not covered in this review. Major topics addressed include dye-sensitized solar cells, quantum-dot-sensitized solar cells, and p-n junction solar cells.

Linking climate projections to performance: A yield-based decision scaling assessment of a large urban water resources system

NASA Astrophysics Data System (ADS)

Turner, Sean W. D.; Marlow, David; Ekström, Marie; Rhodes, Bruce G.; Kularathna, Udaya; Jeffrey, Paul J.

2014-04-01

Despite a decade of research into climate change impacts on water resources, the scientific community has delivered relatively few practical methodological developments for integrating uncertainty into water resources system design. This paper presents an application of the "decision scaling" methodology for assessing climate change impacts on water resources system performance and asks how such an approach might inform planning decisions. The decision scaling method reverses the conventional ethos of climate impact assessment by first establishing the climate conditions that would compel planners to intervene. Climate model projections are introduced at the end of the process to characterize climate risk in such a way that avoids the process of propagating those projections through hydrological models. Here we simulated 1000 multisite synthetic monthly streamflow traces in a model of the Melbourne bulk supply system to test the sensitivity of system performance to variations in streamflow statistics. An empirical relation was derived to convert decision-critical flow statistics to climatic units, against which 138 alternative climate projections were plotted and compared. We defined the decision threshold in terms of a system yield metric constrained by multiple performance criteria. Our approach allows for fast and simple incorporation of demand forecast uncertainty and demonstrates the reach of the decision scaling method through successful execution in a large and complex water resources system. Scope for wider application in urban water resources planning is discussed.

Low-scale warped extra dimension and its predilection for multiple top quarks

NASA Astrophysics Data System (ADS)

Jung, Sunghoon; Wells, James D.

2010-11-01

Within warped extra dimension models that explain flavor through geometry, flavor changing neutral current constraints generally force the Kaluza-Klein scale to be above many TeV. This creates tension with a natural electroweak scale. On the other hand, a much lower scale compatible with precision electroweak and flavor changing neutral current constraints is allowed if we decouple the Kaluza-Klein states of Standard Model gauge bosons from light fermions ( c light ≃ c b ≃ 0 .5 bulk mass parameters). The main signature for this approach is four top quark production via the Kaluza-Klein excitations’ strong coupling to top quarks. We study single lepton, like-sign dilepton, and trilepton observables of four-top events at the Large Hadron Collider. The like-sign dilepton signature typically has the largest discovery potential for a strongly coupled right-handed top case ( M KK ˜ 2 - 2 .5 TeV), while single lepton is the better when the left-handed top couples most strongly ( M KK ˜ 2 TeV). We also describe challenging lepton-jet collimation issues in the like-sign dilepton and trilepton channels. An alternative single lepton observable is considered which takes advantage of the many bottom quarks in the final state. Although searches of other particles may compete, we find that four top production via Kaluza-Klein gluons is most promising in a large region of this parameter space.

Conformational Fluctuations in G-Protein-Coupled Receptors

NASA Astrophysics Data System (ADS)

Brown, Michael F.

2014-03-01

G-protein-coupled receptors (GPCRs) comprise almost 50% of pharmaceutical drug targets, where rhodopsin is an important prototype and occurs naturally in a lipid membrane. Rhodopsin photoactivation entails 11-cis to all-trans isomerization of the retinal cofactor, yielding an equilibrium between inactive Meta-I and active Meta-II states. Two important questions are: (1) Is rhodopsin is a simple two-state switch? Or (2) does isomerization of retinal unlock an activated conformational ensemble? For an ensemble-based activation mechanism (EAM) a role for conformational fluctuations is clearly indicated. Solid-state NMR data together with theoretical molecular dynamics (MD) simulations detect increased local mobility of retinal after light activation. Resultant changes in local dynamics of the cofactor initiate large-scale fluctuations of transmembrane helices that expose recognition sites for the signal-transducing G-protein. Time-resolved FTIR studies and electronic spectroscopy further show the conformational ensemble is strongly biased by the membrane lipid composition, as well as pH and osmotic pressure. A new flexible surface model (FSM) describes how the curvature stress field of the membrane governs the energetics of active rhodopsin, due to the spontaneous monolayer curvature of the lipids. Furthermore, influences of osmotic pressure dictate that a large number of bulk water molecules are implicated in rhodopsin activation. Around 60 bulk water molecules activate rhodopsin, which is much larger than the number of structural waters seen in X-ray crystallography, or inferred from studies of bulk hydrostatic pressure. Conformational selection and promoting vibrational motions of rhodopsin lead to activation of the G-protein (transducin). Our biophysical data give a paradigm shift in understanding GPCR activation. The new view is: dynamics and conformational fluctuations involve an ensemble of substates that activate the cognate G-protein in the amplified visual response.

Quantum spin Hall insulator BiXH (XH = OH, SH) monolayers with a large bulk band gap.

PubMed

Hu, Xing-Kai; Lyu, Ji-Kai; Zhang, Chang-Wen; Wang, Pei-Ji; Ji, Wei-Xiao; Li, Ping

2018-05-16

A large bulk band gap is critical for the application of two-dimensional topological insulators (TIs) in spintronic devices operating at room temperature. On the basis of first-principles calculations, we predict BiXH (X = OH, SH) monolayers as TIs with an extraordinarily large bulk gap of 820 meV for BiOH and 850 meV for BiSH, and propose a tight-binding model considering spin-orbit coupling to describe the electronic properties of BiXH. These large gaps are entirely due to the strong spin-orbit interaction related to the pxy orbitals of the Bi atoms of the honeycomb lattice. The orbital filtering mechanism can be used to understand the topological properties of BiXH. The XH groups simply remove one branch of orbitals (pz of Bi) and reduce the trivial 6-band lattice into a 4-band, which is topologically non-trivial. The topological characteristics of BiXH monolayers are confirmed by nonzero topological invariant Z2 and a single pair of gapless helical edge states in the bulk gap. Owing to these features, the BiXH monolayers of the large-gap TIs are an ideal platform to realize many exotic phenomena and fabricate new quantum devices working at room temperature.

Surface adsorption of oppositely charged C14TAB-PAMPS mixtures at the air/water interface and the impact on foam film stability.

PubMed

Fauser, Heiko; von Klitzing, Regine; Campbell, Richard A

2015-01-08

We have studied the oppositely charged polyelectrolyte/surfactant mixture of poly(acrylamidomethylpropanesulfonate) sodium salt (PAMPS) and tetradecyl trimethylammonium bromide (C14TAB) using a combination of neutron reflectivity and ellipsometry measurements. The interfacial composition was determined using three different analysis methods involving the two techniques for the first time. The bulk surfactant concentration was fixed at a modest value while the bulk polyelectrolyte concentration was varied over a wide range. We reveal complex changes in the surface adsorption behavior. Mixtures with low bulk PAMPS concentrations result in the components interacting synergistically in charge neutral layers at the air/water interface. At the bulk composition where PAMPS and C14TAB are mixed in an equimolar charge ratio in the bulk, we observe a dramatic drop in the surfactant surface excess to leave a large excess of polyelectrolyte at the interface, which we infer to have loops in its interfacial structure. Further increase of the bulk PAMPS concentration leads to a more pronounced depletion of material from the surface. Mixtures containing a large excess of PAMPS in the bulk showed enhanced adsorption, which is attributed to the large increase in total ionic strength of the system and screening of the surfactant headgroup charges. The data are compared to our former results on PAMPS/C14TAB mixtures [Kristen et al. J. Phys. Chem. B, 2009, 23, 7986]. A peak in the surface tension is rationalized in terms of the changing surface adsorption and, unlike in more concentrated systems, is unrelated to bulk precipitation. Also, a comparison between the determined interfacial composition with zeta potential and foam film stability data shows that the highest film stability occurs when there is enhanced synergistic adsorption of both components at the interface due to charge screening when the total ionic strength of the system is highest. The additional contribution to the foam stability of the negatively charged polyelectrolyte within the film bulk is also discussed.

Wall roughness induces asymptotic ultimate turbulence

NASA Astrophysics Data System (ADS)

Zhu, Xiaojue; Verschoof, Ruben A.; Bakhuis, Dennis; Huisman, Sander G.; Verzicco, Roberto; Sun, Chao; Lohse, Detlef

2018-04-01

Turbulence governs the transport of heat, mass and momentum on multiple scales. In real-world applications, wall-bounded turbulence typically involves surfaces that are rough; however, characterizing and understanding the effects of wall roughness on turbulence remains a challenge. Here, by combining extensive experiments and numerical simulations, we examine the paradigmatic Taylor-Couette system, which describes the closed flow between two independently rotating coaxial cylinders. We show how wall roughness greatly enhances the overall transport properties and the corresponding scaling exponents associated with wall-bounded turbulence. We reveal that if only one of the walls is rough, the bulk velocity is slaved to the rough side, due to the much stronger coupling to that wall by the detaching flow structures. If both walls are rough, the viscosity dependence is eliminated, giving rise to asymptotic ultimate turbulence—the upper limit of transport—the existence of which was predicted more than 50 years ago. In this limit, the scaling laws can be extrapolated to arbitrarily large Reynolds numbers.

Analysis of Helium Segregation on Surfaces of Plasma-Exposed Tungsten

NASA Astrophysics Data System (ADS)

Maroudas, Dimitrios; Hu, Lin; Hammond, Karl; Wirth, Brian

2015-11-01

We report a systematic theoretical and atomic-scale computational study of implanted helium segregation on surfaces of tungsten, which is considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations, including molecular statics to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile helium clusters (of 1-7 He atoms) in the near-surface region are attracted to the surface due to an elastic interaction force. This thermodynamic driving force induces drift fluxes of these mobile clusters toward the surface, facilitating helium segregation. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, at rates much higher than in the bulk material. This cluster dynamics has significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure.

A Mixed-dimensional Model for Determining the Impact of Permafrost Polygonal Ground Degradation on Arctic Hydrology.

NASA Astrophysics Data System (ADS)

Coon, E.; Jan, A.; Painter, S. L.; Moulton, J. D.; Wilson, C. J.

2017-12-01

Many permafrost-affected regions in the Arctic manifest a polygonal patterned ground, which contains large carbon stores and is vulnerability to climate change as warming temperatures drive melting ice wedges, polygon degradation, and thawing of the underlying carbon-rich soils. Understanding the fate of this carbon is difficult. The system is controlled by complex, nonlinear physics coupling biogeochemistry, thermal-hydrology, and geomorphology, and there is a strong spatial scale separation between microtopograpy (at the scale of an individual polygon) and the scale of landscape change (at the scale of many thousands of polygons). Physics-based models have come a long way, and are now capable of representing the diverse set of processes, but only on individual polygons or a few polygons. Empirical models have been used to upscale across land types, including ecotypes evolving from low-centered (pristine) polygons to high-centered (degraded) polygon, and do so over large spatial extent, but are limited in their ability to discern causal process mechanisms. Here we present a novel strategy that looks to use physics-based models across scales, bringing together multiple capabilities to capture polygon degradation under a warming climate and its impacts on thermal-hydrology. We use fine-scale simulations on individual polygons to motivate a mixed-dimensional strategy that couples one-dimensional columns representing each individual polygon through two-dimensional surface flow. A subgrid model is used to incorporate the effects of surface microtopography on surface flow; this model is described and calibrated to fine-scale simulations. And critically, a subsidence model that tracks volume loss in bulk ice wedges is used to alter the subsurface structure and subgrid parameters, enabling the inclusion of the feedbacks associated with polygon degradation. This combined strategy results in a model that is able to capture the key features of polygon permafrost degradation, but in a simulation across a large spatial extent of polygonal tundra.

Shock-wave structure for a polyatomic gas with large bulk viscosity

NASA Astrophysics Data System (ADS)

Kosuge, Shingo; Aoki, Kazuo

2018-02-01

The structure of a standing plane shock wave in a polyatomic gas is investigated on the basis of kinetic theory, with special interest in gases with large bulk viscosities, such as CO2 gas. The ellipsoidal statistical model for a polyatomic gas is employed. First, the shock structure is computed numerically for various upstream Mach numbers and for various (large) values of the ratio of the bulk viscosity to the shear viscosity, and different types of profiles, such as the double-layer structure consisting of a thin upstream layer with a steep change and a much thicker downstream layer with a mild change, are obtained. Then, an asymptotic analysis for large values of the ratio is carried out, and an analytical solution that describes the different types of profiles obtained by the numerical analysis, such as the double-layer structure, correctly is obtained.

Final Report “Electrical and mechanical characterization of rocks at the sub-millimeter scale” DE-SC0000757

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scales, John

The broad purpose of CSM's 6-year (3 years plus renewal) DOE project was to develop and apply new experimental physics technology to the material characterization of rocks at the grain scale or smaller. This is motivated by a knowledge that the bulk chemistry and physics of rocks are strongly influenced by processes occurring at the grain scale: the flow of fluids, cation exchange, the state of cementation of grains, and many more. It may also be possible in some cases to ``upscale'' or homogenize the mesoscopic properties of rocks in order to directly infer the large-scale properties of formations, butmore » that is not our central goal. Understanding the physics and chemistry at the small scale is. During the first 3 years, most effort was devoted to developing and validating the near-field scanning technology. During the 3 year renewal phase, most effort was focused on applying the technology in the labs Professors Batzle (now deceased) in Geophysics and Prasad in Petroleum engineering.« less

Design of a novel automated methanol feed system for pilot-scale fermentation of Pichia pastoris.

PubMed

Hamaker, Kent H; Johnson, Daniel C; Bellucci, Joseph J; Apgar, Kristie R; Soslow, Sherry; Gercke, John C; Menzo, Darrin J; Ton, Christopher

2011-01-01

Large-scale fermentation of Pichia pastoris requires a large volume of methanol feed during the induction phase. However, a large volume of methanol feed is difficult to use in the processing suite because of the inconvenience of constant monitoring, manual manipulation steps, and fire and explosion hazards. To optimize and improve safety of the methanol feed process, a novel automated methanol feed system has been designed and implemented for industrial fermentation of P. pastoris. Details of the design of the methanol feed system are described. The main goals of the design were to automate the methanol feed process and to minimize the hazardous risks associated with storing and handling large quantities of methanol in the processing area. The methanol feed system is composed of two main components: a bulk feed (BF) system and up to three portable process feed (PF) systems. The BF system automatically delivers methanol from a central location to the portable PF system. The PF system provides precise flow control of linear, step, or exponential feed of methanol to the fermenter. Pilot-scale fermentations with linear and exponential methanol feeds were conducted using two Mut(+) (methanol utilization plus) strains, one expressing a recombinant therapeutic protein and the other a monoclonal antibody. Results show that the methanol feed system is accurate, safe, and efficient. The feed rates for both linear and exponential feed methods were within ± 5% of the set points, and the total amount of methanol fed was within 1% of the targeted volume. Copyright © 2011 American Institute of Chemical Engineers (AIChE).

RACORO Continental Boundary Layer Cloud Investigations: 1. Case Study Development and Ensemble Large-Scale Forcings

NASA Technical Reports Server (NTRS)

Vogelmann, Andrew M.; Fridlind, Ann M.; Toto, Tami; Endo, Satoshi; Lin, Wuyin; Wang, Jian; Feng, Sha; Zhang, Yunyan; Turner, David D.; Liu, Yangang;

RACORO continental boundary layer cloud investigations: 1. Case study development and ensemble large-scale forcings

NASA Astrophysics Data System (ADS)

Vogelmann, Andrew M.; Fridlind, Ann M.; Toto, Tami; Endo, Satoshi; Lin, Wuyin; Wang, Jian; Feng, Sha; Zhang, Yunyan; Turner, David D.; Liu, Yangang; Li, Zhijin; Xie, Shaocheng; Ackerman, Andrew S.; Zhang, Minghua; Khairoutdinov, Marat

2015-06-01

Observation-based modeling case studies of continental boundary layer clouds have been developed to study cloudy boundary layers, aerosol influences upon them, and their representation in cloud- and global-scale models. Three 60 h case study periods span the temporal evolution of cumulus, stratiform, and drizzling boundary layer cloud systems, representing mixed and transitional states rather than idealized or canonical cases. Based on in situ measurements from the Routine AAF (Atmospheric Radiation Measurement (ARM) Aerial Facility) CLOWD (Clouds with Low Optical Water Depth) Optical Radiative Observations (RACORO) field campaign and remote sensing observations, the cases are designed with a modular configuration to simplify use in large-eddy simulations (LES) and single-column models. Aircraft measurements of aerosol number size distribution are fit to lognormal functions for concise representation in models. Values of the aerosol hygroscopicity parameter, κ, are derived from observations to be 0.10, which are lower than the 0.3 typical over continents and suggestive of a large aerosol organic fraction. Ensemble large-scale forcing data sets are derived from the ARM variational analysis, European Centre for Medium-Range Weather Forecasts, and a multiscale data assimilation system. The forcings are assessed through comparison of measured bulk atmospheric and cloud properties to those computed in "trial" large-eddy simulations, where more efficient run times are enabled through modest reductions in grid resolution and domain size compared to the full-sized LES grid. Simulations capture many of the general features observed, but the state-of-the-art forcings were limited at representing details of cloud onset, and tight gradients and high-resolution transients of importance. Methods for improving the initial conditions and forcings are discussed. The cases developed are available to the general modeling community for studying continental boundary clouds.

The influence of mesoscopic confinement on the dynamics of imidazolium-based room temperature ionic liquids in polyether sulfone membranes.

PubMed

Thomaz, Joseph E; Bailey, Heather E; Fayer, Michael D

2017-11-21

The structural dynamics of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C n mimNTf 2 , n = 2, 4, 6, 10: ethyl-Emim; butyl-Bmim; hexyl-Hmim; decyl-Dmim) room temperature ionic liquids confined in the pores of polyether sulfone (PES 200) membranes with an average pore size of ∼350 nm and in the bulk liquids were studied. Time correlated single photon counting measurements of the fluorescence of the fluorophore coumarin 153 (C153) were used to observe the time-dependent Stokes shift (solvation dynamics). The solvation dynamics of C153 in the ionic liquids are multiexponential decays. The multiexponential functional form of the decays was confirmed as the slowest decay component of each bulk liquid matches the slowest component of the liquid dynamics measured by optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments, which is single exponential. The fact that the slowest component of the Stokes shift matches the OHD-OKE data in all four liquids identifies this component of the solvation dynamics as arising from the complete structural randomization of the liquids. Although the pores in the PES membranes are large, confinement on the mesoscopic length scale results in substantial slowing of the dynamics, a factor of ∼4, for EmimNTf 2 , with the effect decreasing as the chain length increases. By DmimNTf 2 , the dynamics are virtually indistinguishable from those in the bulk liquid. The rotation relaxation of C153 in the four bulk liquids was also measured and showed strong coupling between the C153 probe and its environment.

The influence of mesoscopic confinement on the dynamics of imidazolium-based room temperature ionic liquids in polyether sulfone membranes

NASA Astrophysics Data System (ADS)

Thomaz, Joseph E.; Bailey, Heather E.; Fayer, Michael D.

2017-11-01

The structural dynamics of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (CnmimNTf2, n = 2, 4, 6, 10: ethyl—Emim; butyl—Bmim; hexyl—Hmim; decyl—Dmim) room temperature ionic liquids confined in the pores of polyether sulfone (PES 200) membranes with an average pore size of ˜350 nm and in the bulk liquids were studied. Time correlated single photon counting measurements of the fluorescence of the fluorophore coumarin 153 (C153) were used to observe the time-dependent Stokes shift (solvation dynamics). The solvation dynamics of C153 in the ionic liquids are multiexponential decays. The multiexponential functional form of the decays was confirmed as the slowest decay component of each bulk liquid matches the slowest component of the liquid dynamics measured by optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments, which is single exponential. The fact that the slowest component of the Stokes shift matches the OHD-OKE data in all four liquids identifies this component of the solvation dynamics as arising from the complete structural randomization of the liquids. Although the pores in the PES membranes are large, confinement on the mesoscopic length scale results in substantial slowing of the dynamics, a factor of ˜4, for EmimNTf2, with the effect decreasing as the chain length increases. By DmimNTf2, the dynamics are virtually indistinguishable from those in the bulk liquid. The rotation relaxation of C153 in the four bulk liquids was also measured and showed strong coupling between the C153 probe and its environment.

The D-material universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elghozi, Thomas; Mavromatos, Nick E.; Sakellariadou, Mairi

In a previous publication by some of the authors (N.E.M., M.S. and M.F.Y.), we have argued that the ''D-material universe'', that is a model of a brane world propagating in a higher-dimensional bulk populated by collections of D-particle stringy defects, provides a model for the growth of large-scale structure in the universe via the vector field in its spectrum. The latter corresponds to D-particle recoil velocity excitations as a result of the interactions of the defects with stringy matter and radiation on the brane world. In this article, we first elaborate further on the results of the previous study onmore » the galactic growth era and analyse the circumstances under which the D-particle recoil velocity fluid may ''mimic'' dark matter in galaxies. A lensing phenomenology is also presented for some samples of galaxies, which previously were known to provide tension for modified gravity (TeVeS) models. The current model is found in agreement with these lensing data. Then we discuss a cosmic evolution for the D-material universe by analysing the conditions under which the late eras of this universe associated with large-scale structure are connected to early epochs, where inflation takes place. It is shown that inflation is induced by dense populations of D-particles in the early universe, with the rôle of the inflaton field played by the condensate of the D-particle recoil-velocity fields under their interaction with relativistic stringy matter, only for sufficiently large brane tensions and low string mass scales compared to the Hubble scale. On the other hand, for large string scales, where the recoil-velocity condensate fields are weak, inflation cannot be driven by the D-particle defects alone. In such cases inflation may be driven by dilaton (or other moduli) fields in the underlying string theory.« less

Self-Consistent Field Theories for the Role of Large Length-Scale Architecture in Polymers

NASA Astrophysics Data System (ADS)

Wu, David

At large length-scales, the architecture of polymers can be described by a coarse-grained specification of the distribution of branch points and monomer types within a molecule. This includes molecular topology (e.g., cyclic or branched) as well as distances between branch points or chain ends. Design of large length-scale molecular architecture is appealing because it offers a universal strategy, independent of monomer chemistry, to tune properties. Non-linear analogs of linear chains differ in molecular-scale properties, such as mobility, entanglements, and surface segregation in blends that are well-known to impact rheological, dynamical, thermodynamic and surface properties including adhesion and wetting. We have used Self-Consistent Field (SCF) theories to describe a number of phenomena associated with large length-scale polymer architecture. We have predicted the surface composition profiles of non-linear chains in blends with linear chains. These predictions are in good agreement with experimental results, including from neutron scattering, on a range of well-controlled branched (star, pom-pom and end-branched) and cyclic polymer architectures. Moreover, the theory allows explanation of the segregation and conformations of branched polymers in terms of effective surface potentials acting on the end and branch groups. However, for cyclic chains, which have no end or junction points, a qualitatively different topological mechanism based on conformational entropy drives cyclic chains to a surface, consistent with recent neutron reflectivity experiments. We have also used SCF theory to calculate intramolecular and intermolecular correlations for polymer chains in the bulk, dilute solution, and trapped at a liquid-liquid interface. Predictions of chain swelling in dilute star polymer solutions compare favorably with existing PRISM theory and swelling at an interface helps explain recent measurements of chain mobility at an oil-water interface. In collaboration with: Renfeng Hu, Colorado School of Mines, and Mark Foster, University of Akron. This work was supported by NSF Grants No. CBET- 0730692 and No. CBET-0731319.

Large Vessel Occlusion Scales Increase Delivery to Endovascular Centers Without Excessive Harm From Misclassifications.

PubMed

Zhao, Henry; Coote, Skye; Pesavento, Lauren; Churilov, Leonid; Dewey, Helen M; Davis, Stephen M; Campbell, Bruce C V

2017-03-01

Clinical large vessel occlusion (LVO) triage scales were developed to identify and bypass LVO to endovascular centers. However, there are concerns that scale misclassification of patients may cause excessive harm. We studied the settings where misclassifications were likely to occur and the consequences of these misclassifications in a representative stroke population. Prospective data were collected from consecutive ambulance-initiated stroke alerts at 2 stroke centers, with patients stratified into typical (LVO with predefined severe syndrome and non-LVO without) or atypical presentations (opposite situations). Five scales (Rapid Arterial Occlusion Evaluation [RACE], Los Angeles Motor Scale [LAMS], Field Assessment Stroke Triage for Emergency Destination [FAST-ED], Prehospital Acute Stroke Severity scale [PASS], and Cincinnati Prehospital Stroke Severity Scale [CPSSS]) were derived from the baseline National Institutes of Health Stroke Scale scored by doctors and analyzed for diagnostic performance compared with imaging. Of a total of 565 patients, atypical presentations occurred in 31 LVO (38% of LVO) and 50 non-LVO cases (10%). Most scales correctly identified >95% of typical presentations but <20% of atypical presentations. Misclassification attributable to atypical presentations would have resulted in 4 M1/internal carotid artery occlusions, with National Institutes of Health Stroke Scale score ≥6 (5% of LVO) being missed and 9 non-LVO infarcts (5%) bypassing the nearest thrombolysis center. Atypical presentations accounted for the bulk of scale misclassifications, but the majority of these misclassifications were not detrimental, and use of LVO scales would significantly increase timely delivery to endovascular centers, with only a small proportion of non-LVO infarcts bypassing the nearest thrombolysis center. Our findings, however, would require paramedics to score as accurately as doctors, and this translation is made difficult by weaknesses in current scales that need to be addressed before widespread adoption. © 2017 American Heart Association, Inc.

Bulk and edge spin transport in topological magnon insulators

NASA Astrophysics Data System (ADS)

Rückriegel, Andreas; Brataas, Arne; Duine, Rembert A.

2018-02-01

We investigate the spin transport properties of a topological magnon insulator, a magnetic insulator characterized by topologically nontrivial bulk magnon bands and protected magnon edge modes located in the bulk band gaps. Employing the Landau-Lifshitz-Gilbert phenomenology, we calculate the spin current driven through a normal metal |topological magnon insulator |normal metal heterostructure by a spin accumulation imbalance between the metals, with and without random lattice defects. We show that bulk and edge transport are characterized by different length scales. This results in a characteristic system size where the magnon transport crosses over from being bulk dominated for small systems to edge dominated for larger systems. These findings are generic and relevant for topological transport in systems of nonconserved bosons.

ESP Toolbox: A Computational Framework for Precise, Scale-Independent Analysis of Bulk Elastic and Seismic Properties

NASA Astrophysics Data System (ADS)

Johnson, S. E.; Vel, S. S.; Cook, A. C.; Song, W. J.; Gerbi, C. C.; Okaya, D. A.

2014-12-01

Owing to the abundance of highly anisotropic minerals in the crust, the Voigt and Reuss bounds on the seismic velocities can be separated by more than 1 km/s. These bounds are determined by modal mineralogy and crystallographic preferred orientations (CPO) of the constituent minerals, but where the true velocities lie between these bounds is determined by other fabric parameters such as the shapes, shape-preferred orientations, and spatial arrangements of grains. Thus, the calculation of accurate bulk stiffness relies on explicitly treating the grain-scale heterogeneity, and the same principle applies at larger scales, for example calculating accurate bulk stiffness for a crustal volume with varying proportions and distributions of folds or shear zones. We have developed stand-alone GUI software - ESP Toolbox - for the calculation of 3D bulk elastic and seismic properties of heterogeneous and polycrystalline materials using image or EBSD data. The GUI includes a number of different homogenization techniques, including Voigt, Reuss, Hill, geometric mean, self-consistent and asymptotic expansion homogenization (AEH) methods. The AEH method, which uses a finite element mesh, is most accurate since it explicitly accounts for elastic interactions of constituent minerals/phases. The user need only specify the microstructure and material properties of the minerals/phases. We use the Toolbox to explore changes in bulk elasticity and related seismic anisotropy caused by specific variables, including: (a) the quartz alpha-beta phase change in rocks with varying proportions of quartz, (b) changes in modal mineralogy and CPO fabric that occur during progressive deformation and metamorphism, and (c) shear zones of varying thickness, abundance and geometry in continental crust. The Toolbox allows rapid sensitivity analysis around these and other variables, and the resulting bulk stiffness matrices can be used to populate volumes for synthetic wave propagation experiments that allow direct visualization of how variables of interest might affect propagation at a variety of scales. Sensitivity analyses also illustrate the value of the more precise AEH method. The ESP Toolbox can be downloaded here: http://umaine.edu/mecheng/faculty-and-staff/senthil-vel/software/

Evaluating the fidelity of CMIP5 models in producing large-scale meteorological patterns over the Northwestern United States

NASA Astrophysics Data System (ADS)

Lintner, B. R.; Loikith, P. C.; Pike, M.; Aragon, C.

2017-12-01

Climate change information is increasingly required at impact-relevant scales. However, most state-of-the-art climate models are not of sufficiently high spatial resolution to resolve features explicitly at such scales. This challenge is particularly acute in regions of complex topography, such as the Pacific Northwest of the United States. To address this scale mismatch problem, we consider large-scale meteorological patterns (LSMPs), which can be resolved by climate models and associated with the occurrence of local scale climate and climate extremes. In prior work, using self-organizing maps (SOMs), we computed LSMPs over the northwestern United States (NWUS) from daily reanalysis circulation fields and further related these to the occurrence of observed extreme temperatures and precipitation: SOMs were used to group LSMPs into 12 nodes or clusters spanning the continuum of synoptic variability over the regions. Here this observational foundation is utilized as an evaluation target for a suite of global climate models from the Fifth Phase of the Coupled Model Intercomparison Project (CMIP5). Evaluation is performed in two primary ways. First, daily model circulation fields are assigned to one of the 12 reanalysis nodes based on minimization of the mean square error. From this, a bulk model skill score is computed measuring the similarity between the model and reanalysis nodes. Next, SOMs are applied directly to the model output and compared to the nodes obtained from reanalysis. Results reveal that many of the models have LSMPs analogous to the reanalysis, suggesting that the models reasonably capture observed daily synoptic states.

The effect of artificial bulk viscosity in simulations of forced compressible turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campos, A.; Morgan, B.

The use of an artificial bulk viscosity for shock stabilization is a common approach employed in turbulence simulations with high-order numerics. The effect of the artificial bulk viscosity is analyzed in the context of large eddy simulations by using as a test case simulations of linearly-forced compressible homogeneous turbulence (Petersen and Livescu, 2010 [12]). This case is unique in that it allows for the specification of a priori target values for total dissipation and ratio of solenoidal to dilatational dissipation. A comparison between these target values and the true predicted levels of dissipation is thus used to investigate the performancemore » of the artificial bulk viscosity. Results show that the artificial bulk viscosity is effective at achieving stable solutions, but also leads to large values of artificial dissipation that outweigh the physical dissipation caused by fluid viscosity. An alternate approach, which employs the artificial thermal conductivity only, shows that the dissipation of dilatational modes is entirely due to the fluid viscosity. However, this method leads to unwanted Gibbs oscillations around the shocklets. The use of shock sensors that further localize the artificial bulk viscosity did not reduce the amount of artificial dissipation introduced by the artificial bulk viscosity. Finally, an improved forcing function that explicitly accounts for the role of the artificial bulk viscosity in the budget of turbulent kinetic energy was explored.« less

The effect of artificial bulk viscosity in simulations of forced compressible turbulence

DOE PAGES

Campos, A.; Morgan, B.

2018-05-17

The use of an artificial bulk viscosity for shock stabilization is a common approach employed in turbulence simulations with high-order numerics. The effect of the artificial bulk viscosity is analyzed in the context of large eddy simulations by using as a test case simulations of linearly-forced compressible homogeneous turbulence (Petersen and Livescu, 2010 [12]). This case is unique in that it allows for the specification of a priori target values for total dissipation and ratio of solenoidal to dilatational dissipation. A comparison between these target values and the true predicted levels of dissipation is thus used to investigate the performancemore » of the artificial bulk viscosity. Results show that the artificial bulk viscosity is effective at achieving stable solutions, but also leads to large values of artificial dissipation that outweigh the physical dissipation caused by fluid viscosity. An alternate approach, which employs the artificial thermal conductivity only, shows that the dissipation of dilatational modes is entirely due to the fluid viscosity. However, this method leads to unwanted Gibbs oscillations around the shocklets. The use of shock sensors that further localize the artificial bulk viscosity did not reduce the amount of artificial dissipation introduced by the artificial bulk viscosity. Finally, an improved forcing function that explicitly accounts for the role of the artificial bulk viscosity in the budget of turbulent kinetic energy was explored.« less

Influence of Processing Additives on Charge-Transfer Time Scales and Sound Velocity in Organic Bulk Heterojunction Films.

PubMed

Kaake, Loren G; Welch, Gregory C; Moses, Daniel; Bazan, Guillermo C; Heeger, Alan J

2012-05-17

The role of processing additives in organic bulk heterojunction thin films was investigated by means of transient absorption spectroscopy. The rate of ultrafast charge transfer was found to increase when a small amount of diiodooctane was used during film formation. In addition, coherent acoustic phonons were observed, and their velocity was determined. A strong correlation between the sound velocity and the charge-transfer time scale was observed, both of which could be explained by a subtle increase in thin film density.

Towards precision constraints on gravity with the Effective Field Theory of Large-Scale Structure

NASA Astrophysics Data System (ADS)

Bose, Benjamin; Koyama, Kazuya; Lewandowski, Matthew; Vernizzi, Filippo; Winther, Hans A.

2018-04-01

We compare analytical computations with numerical simulations for dark-matter clustering, in general relativity and in the normal branch of DGP gravity (nDGP). Our analytical frameword is the Effective Field Theory of Large-Scale Structure (EFTofLSS), which we use to compute the one-loop dark-matter power spectrum, including the resummation of infrared bulk displacement effects. We compare this to a set of 20 COLA simulations at redshifts z = 0, z = 0.5, and z = 1, and fit the free parameter of the EFTofLSS, called the speed of sound, in both ΛCDM and nDGP at each redshift. At one-loop at z = 0, the reach of the EFTofLSS is kreach ≈ 0.14 Mpc‑1 for both ΛCDM and nDGP. Along the way, we compare two different infrared resummation schemes and two different treatments of the time dependence of the perturbative expansion, concluding that they agree to approximately 1% over the scales of interest. Finally, we use the ratio of the COLA power spectra to make a precision measurement of the difference between the speeds of sound in ΛCDM and nDGP, and verify that this is proportional to the modification of the linear coupling constant of the Poisson equation.

Components for Atomistic-to-Continuum Multiscale Modeling of Flow in Micro- and Nanofluidic Systems

DOE PAGES

Adalsteinsson, Helgi; Debusschere, Bert J.; Long, Kevin R.; ...

2008-01-01

Micro- and nanofluidics pose a series of significant challenges for science-based modeling. Key among those are the wide separation of length- and timescales between interface phenomena and bulk flow and the spatially heterogeneous solution properties near solid-liquid interfaces. It is not uncommon for characteristic scales in these systems to span nine orders of magnitude from the atomic motions in particle dynamics up to evolution of mass transport at the macroscale level, making explicit particle models intractable for all but the simplest systems. Recently, atomistic-to-continuum (A2C) multiscale simulations have gained a lot of interest as an approach to rigorously handle particle-levelmore » dynamics while also tracking evolution of large-scale macroscale behavior. While these methods are clearly not applicable to all classes of simulations, they are finding traction in systems in which tight-binding, and physically important, dynamics at system interfaces have complex effects on the slower-evolving large-scale evolution of the surrounding medium. These conditions allow decomposition of the simulation into discrete domains, either spatially or temporally. In this paper, we describe how features of domain decomposed simulation systems can be harnessed to yield flexible and efficient software for multiscale simulations of electric field-driven micro- and nanofluidics.« less

Should bulk cloudwater or fogwater samples obey Henry's law?

NASA Astrophysics Data System (ADS)

Pandis, Spyros N.; Seinfeld, John H.

1991-06-01

Mixing of droplets with different pH that are individually in Henry's law equilibrium with the surrounding atmosphere always results in a bulk mixture that is supersaturated with weak acids like S(IV) and HCOOH, and bases like NH3 with respect to the original atmosphere. High supersaturations result only when the pH of the bulk droplet mixture exceeds the pKa of the species, in which pH range large pH differences among droplets of different sizes lead to large deviations from Henry's law for the bulk mixture. The deviation is shown to depend on the ratio of the arithmetic mean to the harmonic mean of the hydrogen ion concentrations of the droplets with the liquid water content used as weighting factor in the calculation of the means. The theory developed can explain observed discrepancies from Henry's law in atmospheric samples and also other observed phenomena like the reported increase of pH values of bulk aqueous samples during storage.

A longitudinal survey of anti-Ostertagia ostertagi antibody levels in individual and bulk tank milk in two dairy herds in Normandy.

PubMed

Charlier, Johannes; Camuset, Philippe; Claerebout, Edwin; Courtay, Bruno; Vercruysse, Jozef

2007-10-01

The Ostertagia-specific antibody levels in milk were monitored in 2 dairy herds to investigate seasonal variations and the relationship between individual and bulk tank milk antibody levels. Bulk tank and individual milk samples from all lactating animals were collected over a 1-year period at weekly and monthly intervals, respectively. The Ostertagia-specific antibody levels were measured with an indirect ELISA and the test results were expressed as optical density ratios (ODR). A clear seasonal pattern that followed the expected intake of infectious larvae was observed in the individual and bulk tank milk antibody levels of both herds. Within each herd, there was a large variation in the individual ODRs. This variation remained large when the distribution of individual ODRs was plotted according to high and low bulk tank milk ODR categories. The results suggest that the effect of seasonal variations on cut-off levels that predict production responses after anthelmintic control, needs to be assessed.

Dispersion of ferrofluid aggregates in steady flows

NASA Astrophysics Data System (ADS)

Williams, Alicia M.; Vlachos, Pavlos P.

2011-12-01

Using focused shadowgraphs, we investigate steady flows of a magnetically non-susceptible fluid interacting with ferrofluid aggregates comprised of superparamagnetic nanoparticles. The ferrofluid aggregate is retained at a specific site within the flow channel using two different applied magnetic fields. The bulk flow induces shear stresses on the aggregate, which give rise to the development of interfacial disturbances, leading to Kelvin-Helmholtz (K-H) instabilities and shedding of ferrofluid structures. Herein, the effects of bulk Reynolds number, ranging from 100 to 1000, and maximum applied magnetic fields of 1.2 × 105 and 2.4 × 105 A/m are investigated in the context of their impact on dispersion or removal of material from the core aggregate. The aggregate interaction with steady bulk flow reveals three regimes of aggregate dynamics over the span of Reynolds numbers studied: stable, transitional, and shedding. The first regime is characterized by slight aggregate stretching for low Reynolds numbers, with full aggregate retention. As the Reynolds number increases, the aggregate is in-transition between stable and shedding states. This second regime is characterized by significant initial stretching that gives way to small amplitude Kelvin-Helmholtz waves. Higher Reynolds numbers result in ferrofluid shedding, with Strouhal numbers initially between 0.2 and 0.3, wherein large vortical structures are shed from the main aggregate accompanied by precipitous decay of the accumulated ferrofluid aggregate. These behaviors are apparent for both magnetic field strengths, although the transitional Reynolds numbers are different between the cases, as are the characteristic shedding frequencies relative to the same Reynolds number. In the final step of this study, relevant parameters were extracted from the time series dispersion data to comprehensively quantify aggregate mechanics. The aggregate half-life is found to decrease as a function of the Reynolds number following a power law curve and can be scaled for different magnetic fields using the magnetic induction at the inner wall of the vessel. In addition, the decay rate of the ferrofluid is shown to be proportional to the wall shear rate. Finally, a dimensionless parameter, which scales the inertia-driven flow pressures, relative to the applied magnetic pressures, reveals a power law decay relationship with respect to the incident bulk flow.

Continuum theory of phase separation kinetics for active Brownian particles.

PubMed

Stenhammar, Joakim; Tiribocchi, Adriano; Allen, Rosalind J; Marenduzzo, Davide; Cates, Michael E

2013-10-04

Active Brownian particles (ABPs), when subject to purely repulsive interactions, are known to undergo activity-induced phase separation broadly resembling an equilibrium (attraction-induced) gas-liquid coexistence. Here we present an accurate continuum theory for the dynamics of phase-separating ABPs, derived by direct coarse graining, capturing leading-order density gradient terms alongside an effective bulk free energy. Such gradient terms do not obey detailed balance; yet we find coarsening dynamics closely resembling that of equilibrium phase separation. Our continuum theory is numerically compared to large-scale direct simulations of ABPs and accurately accounts for domain growth kinetics, domain topologies, and coexistence densities.

Effect of Interfacial Turbulence and Accommodation Coefficient on CFD Predictions of Pressurization and Pressure Control in Cryogenic Storage Tank

NASA Technical Reports Server (NTRS)

Kassemi, Mohammad; Kartuzova, Olga; Hylton, Sonya

2015-01-01

Laminar models agree closely with the pressure evolution and vapor phase temperature stratification but under-predict liquid temperatures. Turbulent SST k-w and k-e models under-predict the pressurization rate and extent of stratification in the vapor but represent liquid temperature distributions fairly well. These conclusions seem to equally apply to large cryogenic tank simulations as well as small scale simulant fluid pressurization cases. Appropriate turbulent models that represent both interfacial and bulk vapor phase turbulence with greater fidelity are needed. Application of LES models to the tank pressurization problem can serve as a starting point.

Large extra dimensions, sterile neutrinos and solar neutrino data.

PubMed

Caldwell, D O; Mohapatra, R N; Yellin, S J

2001-07-23

Solar, atmospheric, and LSND neutrino oscillation results require a light sterile neutrino, nu(B), which can exist in the bulk of extra dimensions. Solar nu(e), confined to the brane, can oscillate in the vacuum to the zero mode of nu(B) and via successive Mikheyev-Smirnov-Wolfenstein transitions to Kaluza-Klein states of nu(B). This new way to fit solar data is provided by both low and intermediate string scale models. From average rates seen in the three types of solar experiments, the Super-Kamiokande spectrum is predicted with 73% probability, but dips characteristic of the 0.06 mm extra dimension should be seen in the SNO spectrum.

gram-scale metafluids and large area tunable metamaterials: design, fabrication, and nano-optical tomographic characterization (Conference Presentation)

NASA Astrophysics Data System (ADS)

Dionne, Jennifer A.

2016-09-01

Advances in metamaterials and metasurfaces have enabled unprecedented control of light-matter interactions. Metamaterial constituents support high-frequency electric and magnetic dipoles, which can be used as building blocks for new materials capable of negative refraction, electromagnetic cloaking, strong visible-frequency circular dichroism, and enhanced magnetic or chiral transitions in ions and molecules. However, most metamaterials to date have been limited to solid-state, static, narrow-band, and/or small-area structures. Here, we introduce the design, fabrication, and three-dimensional nano-optical characterization of large-area, dynamically-tunable metamaterials and gram-scale metafluids. First, we use transformation optics to design a broadband metamaterial constituent - a metallo-dielectric nanocrescent - characterized by degenerate electric and magnetic dipoles. A periodic array of nanocrescents exhibits large positive and negative refractive indices at optical frequencies, confirmed through simulations of plane wave refraction through a metamaterial prism. Simulations also reveal that the metamaterial optical properties are largely insensitive to the wavelength, orientation and polarization of incident light. Then, we introduce a new tomographic technique, cathodoluminescence (CL) spectroscopic tomography, to probe light-matter interactions in individual nanocrescents with nanometer-scale resolution. Two-dimensional CL maps of the three-dimensional nanostructure are obtained at various orientations, while a filtered back projection is used to reconstruct the CL intensity at each wavelength. The resulting tomograms allow us to locate regions of efficient cathodoluminescence in three dimensions across visible and near-infrared wavelengths, with contributions from material luminescence and radiative decay of electromagnetic eigenmodes. Finally, we demonstrate the fabrication of dynamically tunable large-area metamaterials and gram-scale metafluids, using a combination of colloidal synthesis, protein-directed assembly, self-assembly, etching, and stamping. The electric and magnetic response of the bulk metamaterial and metafluid are directly probed with optical scattering and spectroscopy. Using chemical swelling, these metamaterials exhibit reversible, unity-order refractive index changes that may provide a foundation for new adaptive optical materials in sensing, solar, and display applications.

Scaling-up vaccine production: implementation aspects of a biomass growth observer and controller.

PubMed

Soons, Zita I T A; van den IJssel, Jan; van der Pol, Leo A; van Straten, Gerrit; van Boxtel, Anton J B

2009-04-01

This study considers two aspects of the implementation of a biomass growth observer and specific growth rate controller in scale-up from small- to pilot-scale bioreactors towards a feasible bulk production process for whole-cell vaccine against whooping cough. The first is the calculation of the oxygen uptake rate, the starting point for online monitoring and control of biomass growth, taking into account the dynamics in the gas-phase. Mixing effects and delays are caused by amongst others the headspace and tubing to the analyzer. These gas phase dynamics are modelled using knowledge of the system in order to reconstruct oxygen consumption. The second aspect is to evaluate performance of the monitoring and control system with the required modifications of the oxygen consumption calculation on pilot-scale. In pilot-scale fed-batch cultivation good monitoring and control performance is obtained enabling a doubled concentration of bulk vaccine compared to standard batch production.

Piezoelectric coefficients of bulk 3R transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Konabe, Satoru; Yamamoto, Takahiro

2017-09-01

The piezoelectric properties of bulk transition metal dichalcogenides (TMDCs) with a 3R structure were investigated using first-principles calculations based on density functional theory combined with the Berry phase treatment. Values for the elastic constant Cijkl , the piezoelectric coefficient eijk , and the piezoelectric coefficient dijk are given for bulk 3R-TMDCs (MoS2, MoSe2, WS2, and WSe2). The piezoelectric coefficients of bulk 3R-TMDCs are shown to be sufficiently large or comparable to those of conventional bulk piezoelectric materials such as α-quartz, wurtzite GaN, and wurtzite AlN.

Development of a Bulk-Format System to Harvest, Handle, Store, and Deliver High-Tonnage Low-Moisture Switchgrass Feedstock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Womac, Alvin; Groothuis, Mitch; Westover, Tyler

2013-09-24

This project evaluates and compares comprehensive feedstock logistics systems (FLS), where a FLS is defined to comprehensively span from biomass material standing in a field to conveyance of a uniform, industrial-milled product into the throat of a biomass conversion facility (BCF). Elements of the bulk-format FLS evaluated in this project include: field-standing switchgrass dry chopped into bulk format on the farm, hauled (either loose or bulk compacted) to storage, stored with confining overburden in a protective facility, reclaimed and conveyed to bulk-format discharge, bulk compacted into an ejector trailer, and conveyed as bulk flow into the BCF. In this FLSmore » evaluation, bulk storage bins served as a controlled and sensored proxy for large commercial stacks protected from moisture with a membrane cover.« less

Nonextensive Entropy Approach to Space Plasma Fluctuations and Turbulence

NASA Astrophysics Data System (ADS)

Leubner, M. P.; Vörös, Z.; Baumjohann, W.

Spatial intermittency in fully developed turbulence is an established feature of astrophysical plasma fluctuations and in particular apparent in the interplanetary medium by in situ observations. In this situation, the classical Boltzmann— Gibbs extensive thermo-statistics, applicable when microscopic interactions and memory are short ranged and the environment is a continuous and differentiable manifold, fails. Upon generalization of the entropy function to nonextensivity, accounting for long-range interactions and thus for correlations in the system, it is demonstrated that the corresponding probability distribution functions (PDFs) are members of a family of specific power-law distributions. In particular, the resulting theoretical bi-κ functional reproduces accurately the observed global leptokurtic, non-Gaussian shape of the increment PDFs of characteristic solar wind variables on all scales, where nonlocality in turbulence is controlled via a multiscale coupling parameter. Gradual decoupling is obtained by enhancing the spatial separation scale corresponding to increasing κ-values in case of slow solar wind conditions where a Gaussian is approached in the limit of large scales. Contrary, the scaling properties in the high speed solar wind are predominantly governed by the mean energy or variance of the distribution, appearing as second parameter in the theory. The PDFs of solar wind scalar field differences are computed from WIND and ACE data for different time-lags and bulk speeds and analyzed within the nonextensive theory, where also a particular nonlinear dependence of the coupling parameter and variance with scale arises for best fitting theoretical PDFs. Consequently, nonlocality in fluctuations, related to both, turbulence and its large scale driving, should be related to long-range interactions in the context of nonextensive entropy generalization, providing fundamentally the physical background of the observed scale dependence of fluctuations in intermittent space plasmas.

Scientific goals of the Cooperative Multiscale Experiment (CME)

NASA Technical Reports Server (NTRS)

Cotton, William

1993-01-01

Mesoscale Convective Systems (MCS) form the focus of CME. Recent developments in global climate models, the urgent need to improve the representation of the physics of convection, radiation, the boundary layer, and orography, and the surge of interest in coupling hydrologic, chemistry, and atmospheric models of various scales, have emphasized the need for a broad interdisciplinary and multi-scale approach to understanding and predicting MCS's and their interactions with processes at other scales. The role of mesoscale systems in the large-scale atmospheric circulation, the representation of organized convection and other mesoscale flux sources in terms of bulk properties, and the mutually consistent treatment of water vapor, clouds, radiation, and precipitation, are all key scientific issues concerning which CME will seek to increase understanding. The manner in which convective, mesoscale, and larger scale processes interact to produce and organize MCS's, the moisture cycling properties of MCS's, and the use of coupled cloud/mesoscale models to better understand these processes, are also major objectives of CME. Particular emphasis will be placed on the multi-scale role of MCS's in the hydrological cycle and in the production and transport of chemical trace constituents. The scientific goals of the CME consist of the following: understand how the large and small scales of motion influence the location, structure, intensity, and life cycles of MCS's; understand processes and conditions that determine the relative roles of balanced (slow manifold) and unbalanced (fast manifold) circulations in the dynamics of MCS's throughout their life cycles; assess the predictability of MCS's and improve the quantitative forecasting of precipitation and severe weather events; quantify the upscale feedback of MCS's to the large-scale environment and determine interrelationships between MCS occurrence and variations in the large-scale flow and surface forcing; provide a data base for initialization and verification of coupled regional, mesoscale/hydrologic, mesoscale/chemistry, and prototype mesoscale/cloud-resolving models for prediction of severe weather, ceilings, and visibility; provide a data base for initialization and validation of cloud-resolving models, and for assisting in the fabrication, calibration, and testing of cloud and MCS parameterization schemes; and provide a data base for validation of four dimensional data assimilation schemes and algorithms for retrieving cloud and state parameters from remote sensing instrumentation.

Bulk contribution to magnetotransport properties of low-defect-density Bi2Te3 topological insulator thin films

NASA Astrophysics Data System (ADS)

Ngabonziza, P.; Wang, Y.; Brinkman, A.

2018-04-01

An important challenge in the field of topological materials is to carefully disentangle the electronic transport contribution of the topological surface states from that of the bulk. For Bi2Te3 topological insulator samples, bulk single crystals and thin films exposed to air during fabrication processes are known to be bulk conducting, with the chemical potential in the bulk conduction band. For Bi2Te3 thin films grown by molecular beam epitaxy, we combine structural characterization (transmission electron microscopy), chemical surface analysis as function of time (x-ray photoelectron spectroscopy) and magnetotransport analysis to understand the low defect density and record high bulk electron mobility once charge is doped into the bulk by surface degradation. Carrier densities and electronic mobilities extracted from the Hall effect and the quantum oscillations are consistent and reveal a large bulk carrier mobility. Because of the cylindrical shape of the bulk Fermi surface, the angle dependence of the bulk magnetoresistance oscillations is two dimensional in nature.

Lower continental crust formation through focused flow in km-scale melt conduits: The zoned ultramafic bodies of the Chilas Complex in the Kohistan island arc (NW Pakistan)

NASA Astrophysics Data System (ADS)

Jagoutz, O.; Müntener, O.; Burg, J.-P.; Ulmer, P.; Jagoutz, E.

2006-02-01

Whole-rock and Sm-Nd isotopic data of the main units of the Chilas zoned ultramafic bodies (Kohistan paleo-island arc, NW Pakistan) indicate that ultramafic rocks and gabbronorite sequences stem from a common magma. However, field observations rule out formation of both ultramafic and mafic sequences in terms of gravitational crystal settling in a large magma chamber. Contacts between ultramafic and gabbronorite sequences show emplacement of the dunitic bodies into a semi-consolidated gabbronoritic crystal-mush, which in turn has intruded and reacted with the ultramafic rocks to produce concentric zoning. Field and petrological observations indicate a replacive origin of the dunite. Bulk Mg#'s of dunitic rocks range from 0.87-0.81 indicating that the dunite-forming melt underwent substantial fractionation-differentiation and that percolative fractional crystallization probably generated the dunitic core. The REE chemistry of clinopyroxene in primitive dunite samples and the Nd isotopic composition of ultramafic rocks are in equilibrium with the surrounding gabbronorite. Accordingly, liquids that formed the dunitic rocks and later the mafic sequence derived from a similar depleted source ( ɛNd˜4.8). We propose a mechanism for the comagmatic emplacement, where km-scale ultramafic bodies represent continuous channels reaching down into the upper mantle. The melt-filled porosity in these melt channels diminishes the mean-depth-integrated density difference to the surrounding rocks. Due to buoyancy forces, melt channels raise into the overlying crustal sequence. In the light of such processes, the ultramafic bodies are interpreted as melt channels through which the Chilas gabbronorite sequence was fed. The estimated basaltic-andesitic, low Mg# (˜0.53) bulk composition of the Chilas gabbronorite sequence closely matches estimates of lower crustal compositions. Since the mafic sequence originated from a primary, high Mg# (> 0.7) basaltic arc magma, differentiation of such high Mg# magmas within km-scale isolated melt conduits may explain the "Mg#-gap" between bulk estimates of the continental crust and primary basaltic magmas, a major paradox in the andesite model of crust formation.

7 CFR 70.15 - Equipment and facilities for graders.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Scales graduated in tenths of a pound or less for weighing carcasses, parts, or products individually in containers up to 100 pounds, and test weights for such scales. (4) Scales graduated in one-pound graduation or less for weighing bulk containers of poultry and test weights for such scales. (b) Furnished...

Sample sizes to control error estimates in determining soil bulk density in California forest soils

Treesearch

Youzhi Han; Jianwei Zhang; Kim G. Mattson; Weidong Zhang; Thomas A. Weber

2016-01-01

Characterizing forest soil properties with high variability is challenging, sometimes requiring large numbers of soil samples. Soil bulk density is a standard variable needed along with element concentrations to calculate nutrient pools. This study aimed to determine the optimal sample size, the number of observation (n), for predicting the soil bulk density with a...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glynos, Emmanouil; Johnson, Kyle J.; Frieberg, Bradley

Here, the surface relaxation dynamics of supported star-shaped polymer thin films are shown to be slower than the bulk, persisting up to temperatures at least 50 degrees above the bulk glass transition temperature Tmore » $$bulk\\atop{g}$$. This behavior, exhibited by star-shaped polystyrenes (SPSs) with functionality f = 8 arms and molecular weights per arm M arm < M e (M e is the entanglement molecular weight), is shown by molecular dynamics simulations to be associated with a preferential localization of these macromolecules at the free surface. This new phenomenon is in notable contrast to that of linear chain polymer thin film systems where the surface relaxations are enhanced in relation to the bulk; this enhancement persists only for a limited temperature range above the bulk T$$bulk\\atop{g}$$. Finally, evidence of the slow surface dynamics, compared to the bulk, for temperatures well above T g and at length and time scales not associated with the glass transition has not previously been reported for polymers.« less

Free Surface Relaxations of Star-Shaped Polymer Films

DOE PAGES

Glynos, Emmanouil; Johnson, Kyle J.; Frieberg, Bradley; ...

2017-11-28

Here, the surface relaxation dynamics of supported star-shaped polymer thin films are shown to be slower than the bulk, persisting up to temperatures at least 50 degrees above the bulk glass transition temperature Tmore » $$bulk\\atop{g}$$. This behavior, exhibited by star-shaped polystyrenes (SPSs) with functionality f = 8 arms and molecular weights per arm M arm < M e (M e is the entanglement molecular weight), is shown by molecular dynamics simulations to be associated with a preferential localization of these macromolecules at the free surface. This new phenomenon is in notable contrast to that of linear chain polymer thin film systems where the surface relaxations are enhanced in relation to the bulk; this enhancement persists only for a limited temperature range above the bulk T$$bulk\\atop{g}$$. Finally, evidence of the slow surface dynamics, compared to the bulk, for temperatures well above T g and at length and time scales not associated with the glass transition has not previously been reported for polymers.« less

Microdroplets Accelerate Ring Opening of Epoxides

NASA Astrophysics Data System (ADS)

Lai, Yin-Hung; Sathyamoorthi, Shyam; Bain, Ryan M.; Zare, Richard N.

2018-05-01

The nucleophilic opening of an epoxide is a classic organic reaction that has widespread utility in both academic and industrial applications. We have studied the reaction of limonene oxide with morpholine to form 1-methyl-2-morpholino-4-(prop-1-en-2-yl) cyclohexan-1-ol in bulk solution and in electrosprayed microdroplets with a 1:1 v/ v water/methanol solvent system. We find that even after 90 min at room temperature, there is no product detected by nuclear magnetic resonance spectroscopy in bulk solution whereas in room-temperature microdroplets (2-3 μm in diameter), the yield is already 0.5% in a flight time of 1 ms as observed by mass spectrometry. This constitutes a rate acceleration of 105 in the microdroplet environment, if we assume that as much as 5% of product is formed in bulk after 90 min of reaction time. We examine how the reaction rate depends on droplet size, solvent composition, sheath gas pressure, and applied voltage. These factors profoundly influence the extent of reaction. This dramatic acceleration is not limited to just one system. We have also found that the nucleophilic opening of cis-stilbene oxide by morpholine is similarly accelerated. Such large acceleration factors in reaction rates suggest the use of microdroplets for ring opening of epoxides in other systems, which may have practical significance if such a procedure could be scaled. [Figure not available: see fulltext.

Short-term bulk energy storage system scheduling for load leveling in unit commitment: modeling, optimization, and sensitivity analysis

PubMed Central

Hemmati, Reza; Saboori, Hedayat

2016-01-01

Energy storage systems (ESSs) have experienced a very rapid growth in recent years and are expected to be a promising tool in order to improving power system reliability and being economically efficient. The ESSs possess many potential benefits in various areas in the electric power systems. One of the main benefits of an ESS, especially a bulk unit, relies on smoothing the load pattern by decreasing on-peak and increasing off-peak loads, known as load leveling. These devices require new methods and tools in order to model and optimize their effects in the power system studies. In this respect, this paper will model bulk ESSs based on the several technical characteristics, introduce the proposed model in the thermal unit commitment (UC) problem, and analyze it with respect to the various sensitive parameters. The technical limitations of the thermal units and transmission network constraints are also considered in the model. The proposed model is a Mixed Integer Linear Programming (MILP) which can be easily solved by strong commercial solvers (for instance CPLEX) and it is appropriate to be used in the practical large scale networks. The results of implementing the proposed model on a test system reveal that proper load leveling through optimum storage scheduling leads to considerable operation cost reduction with respect to the storage system characteristics. PMID:27222741

Short-term bulk energy storage system scheduling for load leveling in unit commitment: modeling, optimization, and sensitivity analysis.

PubMed

Hemmati, Reza; Saboori, Hedayat

2016-05-01

Energy storage systems (ESSs) have experienced a very rapid growth in recent years and are expected to be a promising tool in order to improving power system reliability and being economically efficient. The ESSs possess many potential benefits in various areas in the electric power systems. One of the main benefits of an ESS, especially a bulk unit, relies on smoothing the load pattern by decreasing on-peak and increasing off-peak loads, known as load leveling. These devices require new methods and tools in order to model and optimize their effects in the power system studies. In this respect, this paper will model bulk ESSs based on the several technical characteristics, introduce the proposed model in the thermal unit commitment (UC) problem, and analyze it with respect to the various sensitive parameters. The technical limitations of the thermal units and transmission network constraints are also considered in the model. The proposed model is a Mixed Integer Linear Programming (MILP) which can be easily solved by strong commercial solvers (for instance CPLEX) and it is appropriate to be used in the practical large scale networks. The results of implementing the proposed model on a test system reveal that proper load leveling through optimum storage scheduling leads to considerable operation cost reduction with respect to the storage system characteristics.

Temperature uniformity of the bulk medium produced in relativistic heavy-ion collisions

NASA Astrophysics Data System (ADS)

Ray, Lanny

2006-10-01

The success of hydrodynamic models of elliptic flow in relativistic heavy ion collisions is often touted as evidence for rapid thermal equilibration. However, large momentum scale two-particle correlations indicate that a significant fraction of the final-state hadrons retain jet-like correlation structure associated with early stage, non-equilibrated low-Q^2 partons [1]. In addition, correlations on transverse momentum (pt1xpt2) suggest that low-Q^2 parton momentum is partially dissipated causing fluctuations in the effective temperature (thermal and/or collective motion) of the bulk medium[2]. We first show that both global and local temperature fluctuation models describe the available (pt1xpt2) correlation data equally well. Results of an analytical model are then presented which tests the sensitivity of (pt1xpt2) correlations to the first few lower-order cumulants of the two-point temperature distribution for the event ensemble. Unique signatures in the predicted (pt1xpt2) correlations are observed for each cumulant term studied. The prospects for direct measurement of the absolute temperature distribution in the bulk medium produced in relativistic heavy-ion collisions using (pt1xpt2) and other correlation measures are discussed. [1] J. Adams et al., Phys. Rev. C 73, 064907 (2006); J. Phys.G. 32, L37 (2006). [2]J. Adams et al., nucl-ex/0408012.

Micro-scale heat-exchangers for Joule-Thomson cooling.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gross, Andrew John

2014-01-01

This project focused on developing a micro-scale counter flow heat exchangers for Joule-Thomson cooling with the potential for both chip and wafer scale integration. This project is differentiated from previous work by focusing on planar, thin film micromachining instead of bulk materials. A process will be developed for fabricating all the devices mentioned above, allowing for highly integrated micro heat exchangers. The use of thin film dielectrics provides thermal isolation, increasing efficiency of the coolers compared to designs based on bulk materials, and it will allow for wafer-scale fabrication and integration. The process is intended to implement a CFHX asmore » part of a Joule-Thomson cooling system for applications with heat loads less than 1mW. This report presents simulation results and investigation of a fabrication process for such devices.« less

Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale

NASA Astrophysics Data System (ADS)

Koestel, J. K.; Norgaard, T.; Luong, N. M.; Vendelboe, A. L.; Moldrup, P.; Jarvis, N. J.; Lamandé, M.; Iversen, B. V.; Wollesen de Jonge, L.

2013-02-01

It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field site in Silstrup (Denmark) at a sampling distance of approximately 15 m (with a few exceptions), covering an area of approximately 1 ha (60 m × 165 m). For 64 of the 65 investigated soil columns, we observed BTC shapes indicating a strong preferential transport. The strength of preferential transport was positively correlated with the bulk density and the degree of water saturation. The latter suggests that preferential macropore transport was the dominating transport process. Increased bulk densities were presumably related with a decrease in near-saturated hydraulic conductivities and as a consequence to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column scale have to be upscaled when applied to the field scale or larger.

Advances in imaging and quantification of electrical properties at the nanoscale using Scanning Microwave Impedance Microscopy (sMIM)

NASA Astrophysics Data System (ADS)

Friedman, Stuart; Stanke, Fred; Yang, Yongliang; Amster, Oskar

Scanning Microwave Impedance Microscopy (sMIM) is a mode for Atomic Force Microscopy (AFM) enabling imaging of unique contrast mechanisms and measurement of local permittivity and conductivity at the 10's of nm length scale. sMIM has been applied to a variety of systems including nanotubes, nanowires, 2D materials, photovoltaics and semiconductor devices. Early results were largely semi-quantitative. This talk will focus on techniques for extracting quantitative physical parameters such as permittivity, conductivity, doping concentrations and thin film properties from sMIM data. Particular attention will be paid to non-linear materials where sMIM has been used to acquire nano-scale capacitance-voltage curves. These curves can be used to identify the dopant type (n vs p) and doping level in doped semiconductors, both bulk samples and devices. Supported in part by DOE-SBIR DE-SC0009856.

Resonantly enhanced second-harmonic generation using III–V semiconductor all-dielectric metasurfaces

DOE PAGES

Liu, Sheng; Sinclair, Michael B.; Saravi, Sina; ...

2016-08-08

Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scale renders phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using galliummore » arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 10 4 relative to unpatterned GaAs. At the magnetic dipole resonance, we measure an absolute nonlinear conversion efficiency of ~2 × 10 –5 with ~3.4 GW/cm 2 pump intensity. In conclusion, the polarization properties of the SHG reveal that both bulk and surface nonlinearities play important roles in the observed nonlinear process.« less

Local dynamics of glass-forming polystyrene thin films from atomistic simulation

NASA Astrophysics Data System (ADS)

Zhou, Yuxing; Milner, Scott

Despite a wide technological application ranging from protective coatings to organic solar cells, there still no consensus on the mechanism for the glass transition in polymer thin films a manifestation of the infamous glass problem under confinement. Many experimental and computational studies have observed a large deviation of nanoscale dynamical properties in thin films from the corresponding properties in bulk. In this work, we perform extensive united-atom simulations on atactic polystyrene free-standing thin films near the glass transition temperature and focus on the effect of free surface on the local dynamics. We study the segmental dynamics as a function of distance from the surface for different temperatures, from which relaxation time and thereby local Tg is obtained for each layer. We find the dynamics near free surface is not only enhanced but becomes less strongly temperature dependent as Tg is approached compared to the bulk. We find an increasing length scale associated with mobility propagation from the free surface as temperature decreases, but no correlation between local structure and enhanced relaxation rates near the surface, consistent with studies on bead-spring chains.

Energetic mid-IR femtosecond pulse generation by self-defocusing soliton-induced dispersive waves in a bulk quadratic nonlinear crystal.

PubMed

Zhou, Binbin; Guo, Hairun; Bache, Morten

2015-03-09

Generating energetic femtosecond mid-IR pulses is crucial for ultrafast spectroscopy, and currently relies on parametric processes that, while efficient, are also complex. Here we experimentally show a simple alternative that uses a single pump wavelength without any pump synchronization and without critical phase-matching requirements. Pumping a bulk quadratic nonlinear crystal (unpoled LiNbO(3) cut for noncritical phase-mismatched interaction) with sub-mJ near-IR 50-fs pulses, tunable and broadband (∼ 1,000 cm(-1)) mid-IR pulses around 3.0 μm are generated with excellent spatio-temporal pulse quality, having up to 10.5 μJ energy (6.3% conversion). The mid-IR pulses are dispersive waves phase-matched to near-IR self-defocusing solitons created by the induced self-defocusing cascaded nonlinearity. This process is filament-free and the input pulse energy can therefore be scaled arbitrarily by using large-aperture crystals. The technique can readily be implemented with other crystals and laser wavelengths, and can therefore potentially replace current ultrafast frequency-conversion processes to the mid-IR.

General gauge mediation in five dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGarrie, Moritz; Russo, Rodolfo

2010-08-01

We use the ''general gauge mediation'' (GGM) formalism to describe a five-dimensional setup with an S{sup 1}/Z{sub 2} orbifold. We first consider a model independent supersymmetry breaking hidden sector on one boundary and generic chiral matter on another. Using the definition of GGM, the effects of the hidden sector are contained in a set of global symmetry current correlator functions and is mediated through the bulk. We find the gaugino, sfermion and hyperscalar mass formulas for minimal and generalized messengers in different regimes of a large, small and intermediate extra dimension. Then we use the five-dimensional GGM formalism to constructmore » a model in which an SU(5) Intriligator, Seiberg and Shih (ISS) model is located on the hidden boundary. We weakly gauge a global symmetry of the ISS model and associate it with the bulk vector superfield. Compared to four-dimensional GGM, there is a natural way to adjust the gaugino versus sfermion mass ratio by a factor (Ml){sup 2}, where M is a characteristic mass scale of the supersymmetry breaking sector and l is the length of the extra dimension.« less

Quantitative description on structure-property relationships of Li-ion battery materials for high-throughput computations

NASA Astrophysics Data System (ADS)

Wang, Youwei; Zhang, Wenqing; Chen, Lidong; Shi, Siqi; Liu, Jianjun

2017-12-01

Li-ion batteries are a key technology for addressing the global challenge of clean renewable energy and environment pollution. Their contemporary applications, for portable electronic devices, electric vehicles, and large-scale power grids, stimulate the development of high-performance battery materials with high energy density, high power, good safety, and long lifetime. High-throughput calculations provide a practical strategy to discover new battery materials and optimize currently known material performances. Most cathode materials screened by the previous high-throughput calculations cannot meet the requirement of practical applications because only capacity, voltage and volume change of bulk were considered. It is important to include more structure-property relationships, such as point defects, surface and interface, doping and metal-mixture and nanosize effects, in high-throughput calculations. In this review, we established quantitative description of structure-property relationships in Li-ion battery materials by the intrinsic bulk parameters, which can be applied in future high-throughput calculations to screen Li-ion battery materials. Based on these parameterized structure-property relationships, a possible high-throughput computational screening flow path is proposed to obtain high-performance battery materials.

High stability of yellow fever 17D-204 vaccine: a 12-year restrospective analysis of large-scale production.

PubMed

Barban, V; Girerd, Y; Aguirre, M; Gulia, S; Pétiard, F; Riou, P; Barrere, B; Lang, J

2007-04-12

We have retrospectively analyzed 12 bulk lots of yellow fever vaccine Stamaril, produced between 1990 and 2002 and prepared from the same seed lot that has been in continuous use since 1990. All vaccine batches displayed identical genome sequence. Only four nucleotide substitutions were observed, compared to previously published sequence, with no incidence at amino-acid level. Fine analysis of viral plaque size distribution was used as an additional marker for genetic stability and demonstrated a remarkable homogeneity of the viral population. The total virus load, measured by qRT-PCR, was also homogeneous pointing out reproducibility of the vaccine production process. Mice inoculated intracerebrally with the different bulks exhibited a similar average survival time, and ratio between in vitro potency and mouse LD(50) titers remained constant from batch-to-batch. Taken together, these data demonstrate the genetic stability of the strain at mass production level over a period of 12 years and reinforce the generally admitted idea of the safety of YF17D-based vaccines.

Diameter-Dependent Modulus and Melting Behavior in Electrospun Semicrystalline Polymer Fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Y Liu; S Chen; E Zussman

2011-12-31

Confinement of the semicrystalline polymers, poly(ethylene-co-vinyl acetate) (PEVA) and low-density polyethylene (LDPE), produced by electrospinning has been observed to produce fibers with large protrusions, which have not been previously observed in fibers of comparable diameters produced by other methods. SAXS spectra confirmed the crystalline structure and determined that the lamellar spacing was almost unchanged from the bulk. Measurement of the mechanical properties of these fibers, by both shear modulation force microscopy (SMFM) and atomic force acoustic microscopy (AFAM), indicates that the modulii of these fibers increases with decreasing diameter, with the onset at {approx}10 {micro}m, which is an order ofmore » magnitude larger than previously reported. Melting point measurements indicate a decrease of more than 7% in T{sub m}/T{sub 0} (where T{sub m} is the melting point of semicrystalline polymer fibers and T{sub 0} is the melting point of the bulk polymer) for fibers ranging from 4 to 10 {micro}m in diameter. The functional form of the decrease followed a universal curve for PEVA, when scaled with T{sub 0}.« less

Refinement of atomic and magnetic structures using neutron diffraction for synthesized bulk and nano-nickel zinc gallate ferrite

NASA Astrophysics Data System (ADS)

Ata-Allah, S. S.; Balagurov, A. M.; Hashhash, A.; Bobrikov, I. A.; Hamdy, Sh.

2016-01-01

The parent NiFe2O4 and Zn/Ga substituted spinel ferrite powders have been prepared by solid state reaction technique. As a typical example, the Ni0.7Zn0.3Fe1.5Ga0.5O4 sample has been prepared by sol-gel auto combustion method with the nano-scale crystallites size. X-ray and Mössbauer studies were carried out for the prepared samples. Structure and microstructure properties were investigated using the time-of-flight HRFD instrument at the IBR-2 pulsed reactor, at a temperatures range 15-473 K. The Rietveld refinement of the neutron diffraction data revealed that all samples possess cubic symmetry corresponding to the space group Fd3m. Cations distribution show that Ni2+ is a complete inverse spinel ion, while Ga3+ equally distributed between the two A and B-sublattices. The level of microstrains in bulk samples was estimated as very small while the size of coherently scattered domains is quite large. For nano-structured sample the domain size is around 120 Å.

A dark jet dominates the power output of the stellar black hole Cygnus X-1.

PubMed

Gallo, Elena; Fender, Rob; Kaiser, Christian; Russell, David; Morganti, Raffaella; Oosterloo, Tom; Heinz, Sebastian

2005-08-11

Black holes undergoing accretion are thought to emit the bulk of their power in the X-ray band by releasing the gravitational potential energy of the infalling matter. At the same time, they are capable of producing highly collimated jets of energy and particles flowing out of the system with relativistic velocities. Here we show that the 10-solar-mass (10M(o)) black hole in the X-ray binary Cygnus X-1 (refs 3-5) is surrounded by a large-scale (approximately 5 pc in diameter) ring-like structure that appears to be inflated by the inner radio jet. We estimate that in order to sustain the observed emission of the ring, the jet of Cygnus X-1 has to carry a kinetic power that can be as high as the bolometric X-ray luminosity of the binary system. This result may imply that low-luminosity stellar-mass black holes as a whole dissipate the bulk of the liberated accretion power in the form of 'dark', radiatively inefficient relativistic outflows, rather than locally in the X-ray-emitting inflow.

Quantitative description on structure-property relationships of Li-ion battery materials for high-throughput computations.

PubMed

Wang, Youwei; Zhang, Wenqing; Chen, Lidong; Shi, Siqi; Liu, Jianjun

2017-01-01

Li-ion batteries are a key technology for addressing the global challenge of clean renewable energy and environment pollution. Their contemporary applications, for portable electronic devices, electric vehicles, and large-scale power grids, stimulate the development of high-performance battery materials with high energy density, high power, good safety, and long lifetime. High-throughput calculations provide a practical strategy to discover new battery materials and optimize currently known material performances. Most cathode materials screened by the previous high-throughput calculations cannot meet the requirement of practical applications because only capacity, voltage and volume change of bulk were considered. It is important to include more structure-property relationships, such as point defects, surface and interface, doping and metal-mixture and nanosize effects, in high-throughput calculations. In this review, we established quantitative description of structure-property relationships in Li-ion battery materials by the intrinsic bulk parameters, which can be applied in future high-throughput calculations to screen Li-ion battery materials. Based on these parameterized structure-property relationships, a possible high-throughput computational screening flow path is proposed to obtain high-performance battery materials.

Bulk renormalization and particle spectrum in codimension-two brane worlds

NASA Astrophysics Data System (ADS)

Salvio, Alberto

2013-04-01

We study the Casimir energy due to bulk loops of matter fields in codimension-two brane worlds and discuss how effective field theory methods allow us to use this result to renormalize the bulk and brane operators. In the calculation we explicitly sum over the Kaluza-Klein (KK) states with a new convenient method, which is based on a combined use of zeta function and dimensional regularization. Among the general class of models we consider we include a supersymmetric example, 6D gauged chiral supergravity. Although much of our discussion is more general, we treat in some detail a class of compactifications, where the extra dimensions parametrize a rugby ball shaped space with size stabilized by a bulk magnetic flux. The rugby ball geometry requires two branes, which can host the Standard Model fields and carry both tension and magnetic flux (of the bulk gauge field), the leading terms in a derivative expansion. The brane properties have an impact on the KK spectrum and therefore on the Casimir energy as well as on the renormalization of the brane operators. A very interesting feature is that when the two branes carry exactly the same amount of flux, one half of the bulk supersymmetries survives after the compactification, even if the brane tensions are large. We also discuss the implications of these calculations for the natural value of the cosmological constant when the bulk has two large extra dimensions and the bulk supersymmetry is partially preserved (or completely broken).

Numerical Upscaling of Solute Transport in Fractured Porous Media Based on Flow Aligned Blocks

NASA Astrophysics Data System (ADS)

Leube, P.; Nowak, W.; Sanchez-Vila, X.

2013-12-01

High-contrast or fractured-porous media (FPM) pose one of the largest unresolved challenges for simulating large hydrogeological systems. The high contrast in advective transport between fast conduits and low-permeability rock matrix, including complex mass transfer processes, leads to the typical complex characteristics of early bulk arrivals and long tailings. Adequate direct representation of FPM requires enormous numerical resolutions. For large scales, e.g. the catchment scale, and when allowing for uncertainty in the fracture network architecture or in matrix properties, computational costs quickly reach an intractable level. In such cases, multi-scale simulation techniques have become useful tools. They allow decreasing the complexity of models by aggregating and transferring their parameters to coarser scales and so drastically reduce the computational costs. However, these advantages come at a loss of detail and accuracy. In this work, we develop and test a new multi-scale or upscaled modeling approach based on block upscaling. The novelty is that individual blocks are defined by and aligned with the local flow coordinates. We choose a multi-rate mass transfer (MRMT) model to represent the remaining sub-block non-Fickian behavior within these blocks on the coarse scale. To make the scale transition simple and to save computational costs, we capture sub-block features by temporal moments (TM) of block-wise particle arrival times to be matched with the MRMT model. By predicting spatial mass distributions of injected tracers in a synthetic test scenario, our coarse-scale solution matches reasonably well with the corresponding fine-scale reference solution. For predicting higher TM-orders (such as arrival time and effective dispersion), the prediction accuracy steadily decreases. This is compensated to some extent by the MRMT model. If the MRMT model becomes too complex, it loses its effect. We also found that prediction accuracy is sensitive to the choice of the effective dispersion coefficients and on the block resolution. A key advantage of the flow-aligned blocks is that the small-scale velocity field is reproduced quite accurately on the block-scale through their flow alignment. Thus, the block-scale transverse dispersivities remain in the similar magnitude as local ones, and they do not have to represent macroscopic uncertainty. Also, the flow-aligned blocks minimize numerical dispersion when solving the large-scale transport problem.

Search for a new resonance in the boosted di-Higgs to 4 bottom quarks final state at √s = 8 TeV using the ATLAS detector at the Large Hadron Collider

NASA Astrophysics Data System (ADS)

Zhou, Lei

This thesis presents a search for a new, heavy particle decaying to a pair of Higgs bosons in the 4 bottom quarks final state at √ s=8 TeV. ATLAS detector at the Large Hadron Collider. The full data collected by ATLAS in 2012 at √s=8 TeV. is used, corresponding to a total luminosity of 19.5 fb-1. A novel technique, using smaller radius track jet to tag bottom quarks in combination with two large radius calorimeter jets to fully reconstruct boosted event topologies, significantly improves the sensitivity up to the mass scale of 2 TeV. In the absence of an excess, upper limits on the production cross section are set with 95% confidence level, using Kaluza-Klein gravitons in the bulk Randal-Sundrum model with coupling c ≡ k/MPl = 1.0 and 2.0 as benchmarks.

An algorithm for continuum modeling of rocks with multiple embedded nonlinearly-compliant joints [Continuum modeling of elasto-plastic media with multiple embedded nonlinearly-compliant joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurley, R. C.; Vorobiev, O. Y.; Ezzedine, S. M.

Here, we present a numerical method for modeling the mechanical effects of nonlinearly-compliant joints in elasto-plastic media. The method uses a series of strain-rate and stress update algorithms to determine joint closure, slip, and solid stress within computational cells containing multiple “embedded” joints. This work facilitates efficient modeling of nonlinear wave propagation in large spatial domains containing a large number of joints that affect bulk mechanical properties. We implement the method within the massively parallel Lagrangian code GEODYN-L and provide verification and examples. We highlight the ability of our algorithms to capture joint interactions and multiple weakness planes within individualmore » computational cells, as well as its computational efficiency. We also discuss the motivation for developing the proposed technique: to simulate large-scale wave propagation during the Source Physics Experiments (SPE), a series of underground explosions conducted at the Nevada National Security Site (NNSS).« less

An algorithm for continuum modeling of rocks with multiple embedded nonlinearly-compliant joints [Continuum modeling of elasto-plastic media with multiple embedded nonlinearly-compliant joints

DOE PAGES

Hurley, R. C.; Vorobiev, O. Y.; Ezzedine, S. M.

2017-04-06

Here, we present a numerical method for modeling the mechanical effects of nonlinearly-compliant joints in elasto-plastic media. The method uses a series of strain-rate and stress update algorithms to determine joint closure, slip, and solid stress within computational cells containing multiple “embedded” joints. This work facilitates efficient modeling of nonlinear wave propagation in large spatial domains containing a large number of joints that affect bulk mechanical properties. We implement the method within the massively parallel Lagrangian code GEODYN-L and provide verification and examples. We highlight the ability of our algorithms to capture joint interactions and multiple weakness planes within individualmore » computational cells, as well as its computational efficiency. We also discuss the motivation for developing the proposed technique: to simulate large-scale wave propagation during the Source Physics Experiments (SPE), a series of underground explosions conducted at the Nevada National Security Site (NNSS).« less

The Chemical Structure of the Hawaiian Mantle Plume

NASA Astrophysics Data System (ADS)

Ren, Z.; Hirano, N.; Hirata, T.; Takahashi, E.; Ingle, S.

2004-12-01

Numerous geochemical studies of Hawaiian basaltic lavas have shown that the Hawaiian mantle plume is isotopically heterogeneous. However, the distribution and scale of these heterogeneities remain unknown. This is essentially due to the complex interactions created by melting a heterogeneous source, subsequent aggregation of the melts on their way to the surface, and mixing that takes place in shallow magma chambers prior to eruption. In sum, the measured compositions of bulk lavas may represent only _eaverage_f compositions that do not fully reflect the complexity of either the mantle source heterogeneity and/or chemical structure. Melt inclusions, or samples of the local magma frozen in olivine phenocrysts during their formation, are better at recording the complex magmatic history than are the bulk samples. Here, we report major and trace element compositions of olivine-hosted melt inclusions from submarine Haleakala lavas that were collected by 2001-2002 JAMSTEC cruises measured by EPMA and LA-ICP-MS after homogenization at 1250° C, QFM for 20min. Melt inclusions from the submarine Hana Ridge (Haleakala volcano) show large ranges in CaO/Al2O3 (0.92-1.50), TiO2/Na2O (0.79-1.60) and Sr/Nb (14.56-36.60), Zr/Nb (6.48-16.95), ranging from Kilauea-like to Mauna Loa-like compositions within separately-sampled lavas as well as in a single host lava sample. Bulk rocks geochemistry shows that major element composition and trace element ratios such as Zr/Nb, Sr/Nb (Ren et al., 2004a, in press, J. Petrol.) together with Pb, Nd and Sr isotopic ratios (Ren et al., 2004b, submitted to J. Petrol.) of Haleakala shield volcano also display systematic compositional variation changing from a Kilauea-like in the submarine Hana Ridge (main shield stage) to Kilauea-Mauna Loa-like in the subaerial Honomanu stage (late shield stage, data from Chen and Frey, 1991). Some of the compositional variations in melt inclusions in single rocks are wider range than over-all variation observed in bulk rocks. It is important that both Kilauea-like and Mauna Loa-like compositions co-exist in melt inclusions in single submarine Hana Ridge rocks which are identified as Kilauea-like based on bulk geochemistry. These observations are inconsistent with the current interpretation that magma compositions are controlled by concentric zonation of the Hawaiian mantle plume (e.g. Kea component and Loa component), manifested as the Kea trend and the Loa trend volcanoes (e.g. Hauri, 1996; Lassiter et al., 1996). Our new data from olivine-hosted melt inclusions imply that the chemical structure of the Hawaiian mantle plume is significantly more complicated than previously modeled and the length-scale of chemical heterogeneity must be remarkably smaller than estimated based on bulk rock geochemistry.

Faecal bulking efficacy of Australasian breakfast cereals.

PubMed

Monro, John A

2002-01-01

Faecal bulk may play an important role in preventing a range of disorders of the large bowel, but as yet there is little information available on the relative faecal bulking capacities of various foods. Breakfast cereals are often promoted as a good source of potential bulk for 'inner health' because they provide dietary fibre, but their relative abilities to provide faecal bulk per se have not been described. The faecal bulking efficacy of 28 representative Australasian breakfast cereals was therefore measured. A rat model developed for the purpose, and shown to give similar responses as humans to cereal fibres, was used to measure faecal bulking efficacy as increases in fully hydrated faecal weight/100 g diet, based on precise measurements of food intake, faecal dry matter output and faecal water-holding capacity (g water held without stress/g faecal dry matter). Compared to a baseline diet containing 50% sucrose, increments in hydrated faecal weight due to 50% breakfast cereal ranged from slightly negative (Cornflakes, -2 g/100 g diet) to about 80 g/100 g diet (San Bran). Most breakfast cereals increased hydrated faecal weight by between 10 and 20 g/100 g diet from a baseline of 21 +/- 1.5 g/100 g diet, but four products containing high levels of wheat bran had an exceptionally large impact on hydrated faecal weight (increment > 20 g/100 g diet), and the changes resulted more from relative changes in dry matter output than in faecal water retention/gram. However, as faecal water retention was about 2.5 g water/g faecal dry matter on average, increases in dry matter represented large increases in faecal water load. Faecal bulking indices (FBI) for most of the breakfast cereals were less than 20 (wheat bran = 100). The content of wheat bran equivalents for faecal bulk (WBE(fb)) in the breakfast cereals was calculated from FBI. Most breakfast cereals contributed, per serve, less than 10% of a theoretical daily reference value for faecal bulk (DRV(fb) = 63 WBE(fb)/day), which was based on data from human clinical trials and dietary fibre recommendations. Based on the WBE(fb) contribution/serving that would be required to meet the DRV(fb) from the number of servings of dietary fibre sources in the CSIRO 12345+ food and nutrition plan, the results suggest that although some high bran breakfast cereals may contribute substantially to, and many are reasonable sources of, faecal bulk, for most of them, one or two servings at breakfast cannot be relied on to effectively redress shortfalls in faecal bulk elsewhere in the diet.

Correlation Between Bulk Material Defects and Spectroscopic Response in Cadmium Zinc Telluride Detectors

NASA Technical Reports Server (NTRS)

Parker, Bradford H.; Stahle, C. M.; Barthelmy, S. D.; Parsons, A. M.; Tueller, J.; VanSant, J. T.; Munoz, B. F.; Snodgrass, S. J.; Mullinix, R. E.

1999-01-01

One of the critical challenges for large area cadmium zinc telluride (CdZnTe) detector arrays is obtaining material capable of uniform imaging and spectroscopic response. Two complementary nondestructive techniques for characterizing bulk CdZnTe have been developed to identify material with a uniform response. The first technique, infrared transmission imaging, allows for rapid visualization of bulk defects. The second technique, x-ray spectral mapping, provides a map of the material spectroscopic response when it is configured as a planar detector. The two techniques have been used to develop a correlation between bulk defect type and detector performance. The correlation allows for the use of infrared imaging to rapidly develop wafer mining maps. The mining of material free of detrimental defects has the potential to dramatically increase the yield and quality of large area CdZnTe detector arrays.

Predicting Large-scale Effects During Cookoff of Plastic-Bonded Explosives (PBX 9501 PBX 9502 and LX-14)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hobbs, Michael L.; Kaneshige, Michael J.; Erikson, William W.

In this study, we have made reasonable cookoff predictions of large-scale explosive systems by using pressure-dependent kinetics determined from small-scale experiments. Scale-up is determined by properly accounting for pressure generated from gaseous decomposition products and the volume that these reactive gases occupy, e.g. trapped within the explosive, the system, or vented. The pressure effect on the decomposition rates has been determined for different explosives by using both vented and sealed experiments at low densities. Low-density explosives are usually permeable to decomposition gases and can be used in both vented and sealed configurations to determine pressure-dependent reaction rates. In contrast, explosivesmore » that are near the theoretical maximum density (TMD) are not as permeable to decomposition gases, and pressure-dependent kinetics are difficult to determine. Ignition in explosives at high densities can be predicted by using pressure-dependent rates determined from the low-density experiments as long as gas volume changes associated with bulk thermal expansion are also considered. In the current work, cookoff of the plastic-bonded explosives PBX 9501 and PBX 9502 is reviewed and new experimental work on LX-14 is presented. Reactive gases are formed inside these heated explosives causing large internal pressures. The pressure is released differently for each of these explosives. For PBX 9501, permeability is increased and internal pressure is relieved as the nitroplasticizer melts and decomposes. Internal pressure in PBX 9502 is relieved as the material is damaged by cracks and spalling. For LX-14, internal pressure is not relieved until the explosive thermally ignites. The current paper is an extension of work presented at the 26th ICDERS symposium [1].« less

Physical and chemical controls on ore shoots - insights from 3D modeling of an orogenic gold deposit

NASA Astrophysics Data System (ADS)

Vollgger, S. A.; Tomkins, A. G.; Micklethwaite, S.; Cruden, A. R.; Wilson, C. J. L.

2016-12-01

Many ore deposits have irregular grade distributions with localized elongate and well-mineralized rock volumes commonly referred to as ore shoots. The chemical and physical processes that control ore shoot formation are rarely understood, although transient episodes of elevated permeability are thought to be important within the brittle and brittle-ductile crust, due to faulting and fracturing associated with earthquake-aftershock sequences or earthquake swarms. We present data from an orogenic gold deposit in Australia where the bulk of the gold is contained in abundant fine arsenopyrite crystals associated with a fault-vein network within tight upright folds. The deposit-scale fault network is connected to a deeper network of thrust faults (tens of kilometers long). Using 3D implicit modeling of geochemical data, based on radial basis functions, gold grades and gold-arsenic element ratios were interpolated and related to major faults, vein networks and late intrusions. Additionally, downhole bedding measurements were used to model first order (mine-scale) fold structures. The results show that ore shoot plunges are not parallel with mine-scale or regional fold plunges, and that bedding parallel faults related to flexural slip folding play a pivotal role on ore shoot attitudes. 3D fault slip and dilation tendency analysis indicate that fault reactivation and formation of linking faults are associated with large volumes of high-grade ore. We suggest slip events on the large-scale thrust network allowed mineralizing fluids to rapidly migrate over large distances and become supersaturated in elements such as gold, promoting widespread precipitation and high nucleation densities of arsenopyrite upon fluid-rock interaction at trap sites within the deposit.

Water Based Inkjet Material Deposition Of Donor-Acceptor Nanoparticles For Usage In Organic Photovoltaics

NASA Astrophysics Data System (ADS)

Penmetcha, Anirudh Raju

Significant efficiency increases are being made for bulk heterojunction organic photovoltaic prototype devices with world records at 11%. However the chlorinated solvents most frequently used in prototype manufacture would cause local health and safety concerns or large scale environmental pollution upon expansion of these techniques for commercialization. Moreover, research to bridge prototype and large-scale production of these solar cells is still in its infancy. Most prototype devices are made in inert glove box environments using spin-coating. There is a need to develop a non-toxic ink and incorporate it into a material deposition system that can be used in mass production. In this thesis, P3HT:PCBM organic photovoltaic devices were fabricated with the help of inkjet printing. P3HT:PCBM blends were dissolved in organic solvent systems, and this solution was used as the ink for the printer. The "coffee-ring effect" as well as the effect of inkjet printing parameters on film formation were highlighted - thus the inkjet printing method was validated as a stepping stone between lab-scale production of OPVs and large-scale roll-to-roll manufacturing. To address the need of a non-toxic ink, P3HT:PCBM blends were then dispersed in water, using the miniemulsion method. The nanoparticles were characterized for their size, as well as the blending between the P3HT and PCBM within the nanoparticle. These dispersions were then converted into inks. Finally, these nanoparticle inks were inkjet-printed to fabricate OPV devices. Based on the results obtained here, tentative "next steps" have been outlined in order to improve upon this research work, in the future.

Bulk Fuel: Actions Needed to Improve DODs Fuel Consumption Budget Data

DTIC Science & Technology

2016-09-01

BULK FUEL Actions Needed to Improve DOD’s Fuel Consumption Budget Data Report to Congressional Committees...16-644, a report to congressional committees. September 2016 BULK FUEL Actions Needed to Improve DOD’s Fuel Consumption Budget Data What GAO...of about $10.1 billion in fiscal year 2015 but differed from budget estimates, which officials largely attributed to changes in operations and

Microfluidic and nanofluidic phase behaviour characterization for industrial CO2, oil and gas.

PubMed

Bao, Bo; Riordon, Jason; Mostowfi, Farshid; Sinton, David

2017-08-08

Microfluidic systems that leverage unique micro-scale phenomena have been developed to provide rapid, accurate and robust analysis, predominantly for biomedical applications. These attributes, in addition to the ability to access high temperatures and pressures, have motivated recent expanded applications in phase measurements relevant to industrial CO 2 , oil and gas applications. We here present a comprehensive review of this exciting new field, separating microfluidic and nanofluidic approaches. Microfluidics is practical, and provides similar phase properties analysis to established bulk methods with advantages in speed, control and sample size. Nanofluidic phase behaviour can deviate from bulk measurements, which is of particular relevance to emerging unconventional oil and gas production from nanoporous shale. In short, microfluidics offers a practical, compelling replacement of current bulk phase measurement systems, whereas nanofluidics is not practical, but uniquely provides insight into phase change phenomena at nanoscales. Challenges, trends and opportunities for phase measurements at both scales are highlighted.

Tensor network state correspondence and holography

NASA Astrophysics Data System (ADS)

Singh, Sukhwinder

2018-01-01

In recent years, tensor network states have emerged as a very useful conceptual and simulation framework to study quantum many-body systems at low energies. In this paper, we describe a particular way in which any given tensor network can be viewed as a representation of two different quantum many-body states. The two quantum many-body states are said to correspond to each other by means of the tensor network. We apply this "tensor network state correspondence"—a correspondence between quantum many-body states mediated by tensor networks as we describe—to the multi-scale entanglement renormalization ansatz (MERA) representation of ground states of one dimensional (1D) quantum many-body systems. Since the MERA is a 2D hyperbolic tensor network (the extra dimension is identified as the length scale of the 1D system), the two quantum many-body states obtained from the MERA, via tensor network state correspondence, are seen to live in the bulk and on the boundary of a discrete hyperbolic geometry. The bulk state so obtained from a MERA exhibits interesting features, some of which caricature known features of the holographic correspondence of String theory. We show how (i) the bulk state admits a description in terms of "holographic screens", (ii) the conformal field theory data associated with a critical ground state can be obtained from the corresponding bulk state, in particular, how pointlike boundary operators are identified with extended bulk operators. (iii) We also present numerical results to illustrate that bulk states, dual to ground states of several critical spin chains, have exponentially decaying correlations, and that the bulk correlation length generally decreases with increase in central charge for these spin chains.

Analysis of Thermal Structure of Arctic Lakes at Local and Regional Scales Using in Situ and Multidate Landsat-8 Data

NASA Astrophysics Data System (ADS)

Huang, Yan; Liu, Hongxing; Hinkel, Kenneth; Yu, Bailang; Beck, Richard; Wu, Jianping

2017-11-01

The Arctic coastal plain is covered with numerous thermokarst lakes. These lakes are closely linked to climate and environmental change through their heat and water budgets. We examined the intralake thermal structure at the local scale and investigated the water temperature pattern of lakes at the regional scale by utilizing extensive in situ measurements and multidate Landsat-8 remote sensing data. Our analysis indicates that the lake skin temperatures derived from satellite thermal sensors during most of the ice-free summer period effectively represent the lake bulk temperature because the lakes are typically well-mixed and without significant vertical stratification. With the relatively high-resolution Landsat-8 thermal data, we were able to quantitatively examine intralake lateral temperature differences and gradients in relation to geographical location, topography, meteorological factors, and lake morphometry for the first time. Our results suggest that wind speed and direction not only control the vertical stratification but also influences lateral differences and gradients of lake surface temperature. Wind can considerably reduce the intralake temperature gradient. Interestingly, we found that geographical location (latitude, longitude, distance to the ocean) and lake morphometry (surface size, depth, volume) not only control lake temperature regionally but also affect the lateral temperature gradient and homogeneity level within each individual lake. For the Arctic coastal plain, at regional scales, inland and southern lakes tend to have larger horizontal temperature differences and gradients compared to coastal and northern lakes. At local scales, large and shallow lakes tend to have large lateral temperature differences relative to small and deep lakes.

Parameterizing a Large-scale Water Balance Model in Regions with Sparse Data: The Tigris-Euphrates River Basins as an Example

NASA Astrophysics Data System (ADS)

Flint, A. L.; Flint, L. E.

2010-12-01

The characterization of hydrologic response to current and future climates is of increasing importance to many countries around the world that rely heavily on changing and uncertain water supplies. Large-scale models that can calculate a spatially distributed water balance and elucidate groundwater recharge and surface water flows for large river basins provide a basis of estimates of changes due to future climate projections. Unfortunately many regions in the world have very sparse data for parameterization or calibration of hydrologic models. For this study, the Tigris and Euphrates River basins were used for the development of a regional water balance model at 180-m spatial scale, using the Basin Characterization Model, to estimate historical changes in groundwater recharge and surface water flows in the countries of Turkey, Syria, Iraq, Iran, and Saudi Arabia. Necessary input parameters include precipitation, air temperature, potential evapotranspiration (PET), soil properties and thickness, and estimates of bulk permeability from geologic units. Data necessary for calibration includes snow cover, reservoir volumes (from satellite data and historic, pre-reservoir elevation data) and streamflow measurements. Global datasets for precipitation, air temperature, and PET were available at very large spatial scales (50 km) through the world scale databases, finer scale WorldClim climate data, and required downscaling to fine scales for model input. Soils data were available through world scale soil maps but required parameterization on the basis of textural data to estimate soil hydrologic properties. Soil depth was interpreted from geomorphologic interpretation and maps of quaternary deposits, and geologic materials were categorized from generalized geologic maps of each country. Estimates of bedrock permeability were made on the basis of literature and data on driller’s logs and adjusted during calibration of the model to streamflow measurements where available. Results of historical water balance calculations throughout the Tigris and Euphrates River basins will be shown along with details of processing input data to provide spatial continuity and downscaling. Basic water availability analysis for recharge and runoff is readily available from a determinisitic solar radiation energy balance model and a global potential evapotranspiration model and global estimates of precipitation and air temperature. Future climate estimates can be readily applied to the same water and energy balance models to evaluate future water availability for countries around the globe.

Tailoring Magnetic Properties in Bulk Nanostructured Solids

NASA Astrophysics Data System (ADS)

Morales, Jason Rolando

Important magnetic properties and behaviors such as coercivity, remanence, susceptibility, energy product, and exchange coupling can be tailored by controlling the grain size, composition, and density of bulk magnetic materials. At nanometric length scales the grain size plays an increasingly important role since magnetic domain behavior and grain boundary concentration determine bulk magnetic behavior. This has spurred a significant amount of work devoted to developing magnetic materials with nanometric features (thickness, grain/crystallite size, inclusions or shells) in 0D (powder), 1D (wires), and 2D (thin films) materials. Large 3D nanocrystalline materials are more suitable for many applications such as permanent magnets, magneto-optical Faraday isolators etc. Yet there are relatively few successful demonstrations of 3D magnetic materials with nanoscale influenced properties available in the literature. Making dense 3D bulk materials with magnetic nanocrystalline microstructures is a challenge because many traditional densification techniques (HIP, pressureless sintering, etc.) move the microstructure out of the "nano" regime during densification. This dissertation shows that the Current Activated Pressure Assisted Densification (CAPAD) method, also known as spark plasma sintering, can be used to create dense, bulk, magnetic, nanocrystalline solids with varied compositions suited to fit many applications. The results of my research will first show important implications for the use of CAPAD for the production of exchange-coupled nanocomposite magnets. Decreases in grain size were shown to have a significant role in increasing the magnitude of exchange bias. Second, preferentially ordered bulk magnetic materials were produced with highly anisotropic material properties. The ordered microstructure resulted in changing magnetic property magnitudes (ex. change in coercivity by almost 10x) depending on the relative orientation (0° vs. 90°) of an externally applied magnetic field to the sample. Third, a dense magneto-optical material (rare earth oxide) was produced that rotates transmitted polarized light under an externally applied magnetic field, called the Faraday Effect. The magnitude of the rare earth oxide Faraday Effect surpasses that of the current market leader (terbium gallium garnet) in Faraday isolators by ˜2.24x.

Application of a fluidized bed reactor charged with aragonite for control of alkalinity, pH and carbon dioxide in marine recirculating aquaculture systems

USGS Publications Warehouse

Paul S Wills, PhD; Pfeiffer, Timothy; Baptiste, Richard; Watten, Barnaby J.

2016-01-01

Control of alkalinity, dissolved carbon dioxide (dCO2), and pH are critical in marine recirculating aquaculture systems (RAS) in order to maintain health and maximize growth. A small-scale prototype aragonite sand filled fluidized bed reactor was tested under varying conditions of alkalinity and dCO2 to develop and model the response of dCO2 across the reactor. A large-scale reactor was then incorporated into an operating marine recirculating aquaculture system to observe the reactor as the system moved toward equilibrium. The relationship between alkalinity dCO2, and pH across the reactor are described by multiple regression equations. The change in dCO2 across the small-scale reactor indicated a strong likelihood that an equilibrium alkalinity would be maintained by using a fluidized bed aragonite reactor. The large-scale reactor verified this observation and established equilibrium at an alkalinity of approximately 135 mg/L as CaCO3, dCO2 of 9 mg/L, and a pH of 7.0 within 4 days that was stable during a 14 day test period. The fluidized bed aragonite reactor has the potential to simplify alkalinity and pH control, and aid in dCO2 control in RAS design and operation. Aragonite sand, purchased in bulk, is less expensive than sodium bicarbonate and could reduce overall operating production costs.

Phenomenological constraints on the bulk viscosity of QCD

NASA Astrophysics Data System (ADS)

Paquet, Jean-François; Shen, Chun; Denicol, Gabriel; Jeon, Sangyong; Gale, Charles

2017-11-01

While small at very high temperature, the bulk viscosity of Quantum Chromodynamics is expected to grow in the confinement region. Although its precise magnitude and temperature-dependence in the cross-over region is not fully understood, recent theoretical and phenomenological studies provided evidence that the bulk viscosity can be sufficiently large to have measurable consequences on the evolution of the quark-gluon plasma. In this work, a Bayesian statistical analysis is used to establish probabilistic constraints on the temperature-dependence of bulk viscosity using hadronic measurements from RHIC and LHC.

A numerically efficient finite element hydroelastic analysis. Volume 2: Implementation in NASTRAN, part 1

NASA Technical Reports Server (NTRS)

Coppolino, R. N.

1974-01-01

Details are presented of the implementation of the new formulation into NASTRAN including descriptions of the DMAP statements required for conversion of the program and details pertaining to problem definition and bulk data considerations. Details of the current 1/8-scale space shuttle external tank mathematical model, numerical results and analysis/test comparisons are also presented. The appendices include a description and listing of a FORTRAN program used to develop harmonic transformation bulk data (multipoint constraint statements) and sample bulk data information for a number of hydroelastic problems.

Cost-Efficient Storage of Cryogens

NASA Technical Reports Server (NTRS)

Fesmire, J. E.; Sass, J. P.; Nagy, Z.; Sojoumer, S. J.; Morris, D. L.; Augustynowicz, S. D.

2007-01-01

NASA's cryogenic infrastructure that supports launch vehicle operations and propulsion testing is reaching an age where major refurbishment will soon be required. Key elements of this infrastructure are the large double-walled cryogenic storage tanks used for both space vehicle launch operations and rocket propulsion testing at the various NASA field centers. Perlite powder has historically been the insulation material of choice for these large storage tank applications. New bulk-fill insulation materials, including glass bubbles and aerogel beads, have been shown to provide improved thermal and mechanical performance. A research testing program was conducted to investigate the thermal performance benefits as well as to identify operational considerations and associated risks associated with the application of these new materials in large cryogenic storage tanks. The program was divided into three main areas: material testing (thermal conductivity and physical characterization), tank demonstration testing (liquid nitrogen and liquid hydrogen), and system studies (thermal modeling, economic analysis, and insulation changeout). The results of this research work show that more energy-efficient insulation solutions are possible for large-scale cryogenic storage tanks worldwide and summarize the operational requirements that should be considered for these applications.

Improving Representation of Convective Transport for Scale-Aware Parameterization – Part I: Convection and Cloud Properties Simulated with Spectral Bin and Bulk Microphysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man

2015-04-27

The ultimate goal of this study is to improve representation of convective transport by cumulus parameterization for meso-scale and climate models. As Part I of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in mid-latitude continent and tropical regions using the Weather Research and Forecasting (WRF) model with spectral-bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation, vertical velocity of convective cores, and the vertically decreasing trend of radar reflectivitymore » than MOR and MY2, and therefore will be used for analysis of scale-dependence of eddy transport in Part II. The common features of the simulations for all convective systems are (1) the model tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates radar reflectivity in convective cores (SBM predicts smaller radar reflectivity but does not remove the large overestimation); and (3) the model performs better for mid-latitude convective systems than tropical system. The modeled mass fluxes of the mid latitude systems are not sensitive to microphysics schemes, but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes.« less

Unstructured-grid coastal ocean modelling in Southern Adriatic and Northern Ionian Seas

NASA Astrophysics Data System (ADS)

Federico, Ivan; Pinardi, Nadia; Coppini, Giovanni; Oddo, Paolo

2016-04-01

The Southern Adriatic Northern Ionian coastal Forecasting System (SANIFS) is a short-term forecasting system based on unstructured grid approach. The model component is built on SHYFEM finite element three-dimensional hydrodynamic model. The operational chain exploits a downscaling approach starting from the Mediterranean oceanographic-scale model MFS (Mediterranean Forecasting System, operated by INGV). The implementation set-up has been designed to provide accurate hydrodynamics and active tracer processes in the coastal waters of Southern Eastern Italy (Apulia, Basilicata and Calabria regions), where the model is characterized by a variable resolution in range of 50-500 m. The horizontal resolution is also high in open-sea areas, where the elements size is approximately 3 km. The model is forced: (i) at the lateral open boundaries through a full nesting strategy directly with the MFS (temperature, salinity, non-tidal sea surface height and currents) and OTPS (tidal forcing) fields; (ii) at surface through two alternative atmospheric forcing datasets (ECMWF and COSMOME) via MFS-bulk-formulae. Given that the coastal fields are driven by a combination of both local/coastal and deep ocean forcings propagating along the shelf, the performance of SANIFS was verified first (i) at the large and shelf-coastal scales by comparing with a large scale CTD survey and then (ii) at the coastal-harbour scale by comparison with CTD, ADCP and tide gauge data. Sensitivity tests were performed on initialization conditions (mainly focused on spin-up procedures) and on surface boundary conditions by assessing the reliability of two alternative datasets at different horizontal resolution (12.5 and 7 km). The present work highlights how downscaling could improve the simulation of the flow field going from typical open-ocean scales of the order of several km to the coastal (and harbour) scales of tens to hundreds of meters.

Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

NASA Technical Reports Server (NTRS)

Smialek, James L.

2008-01-01

Alumina scale adhesion to high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However, adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for thermal barrier coatings (TBCs), culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylation of aluminum from the alloy interface appears to be the relevant basic reaction.

Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

NASA Technical Reports Server (NTRS)

Smialek, James L.

2008-01-01

Alumina scale adhesion to high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for TBC s, culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylation of aluminum from the alloy interface appears to be the relevant basic reaction.

Symmetry breaking in holographic theories with Lifshitz scaling

NASA Astrophysics Data System (ADS)

Argurio, Riccardo; Hartong, Jelle; Marzolla, Andrea; Naegels, Daniel

2018-02-01

We study holographically Lifshitz-scaling theories with broken symmetries. In order to do this, we set up a bulk action with a complex scalar and a massless vector on a background which consists in a Lifshitz metric and a massive vector. We first study separately the complex scalar and the massless vector, finding a similar pattern in the twopoint functions that we can compute analytically. By coupling the probe complex scalar to the background massive vector we can construct probe actions that are more general than the usual Klein-Gordon action. Some of these actions have Galilean boost symmetry. Finally, in the presence of a symmetry breaking scalar profile in the bulk, we reproduce the expected Ward identities of a Lifshitz-scaling theory with a broken global continuous symmetry. In the spontaneous case, the latter imply the presence of a gapless mode, the Goldstone boson, which will have dispersion relations dictated by the Lifshitz scaling.

Large-scale quantum photonic circuits in silicon

NASA Astrophysics Data System (ADS)

Harris, Nicholas C.; Bunandar, Darius; Pant, Mihir; Steinbrecher, Greg R.; Mower, Jacob; Prabhu, Mihika; Baehr-Jones, Tom; Hochberg, Michael; Englund, Dirk

2016-08-01

Quantum information science offers inherently more powerful methods for communication, computation, and precision measurement that take advantage of quantum superposition and entanglement. In recent years, theoretical and experimental advances in quantum computing and simulation with photons have spurred great interest in developing large photonic entangled states that challenge today's classical computers. As experiments have increased in complexity, there has been an increasing need to transition bulk optics experiments to integrated photonics platforms to control more spatial modes with higher fidelity and phase stability. The silicon-on-insulator (SOI) nanophotonics platform offers new possibilities for quantum optics, including the integration of bright, nonclassical light sources, based on the large third-order nonlinearity (χ(3)) of silicon, alongside quantum state manipulation circuits with thousands of optical elements, all on a single phase-stable chip. How large do these photonic systems need to be? Recent theoretical work on Boson Sampling suggests that even the problem of sampling from e30 identical photons, having passed through an interferometer of hundreds of modes, becomes challenging for classical computers. While experiments of this size are still challenging, the SOI platform has the required component density to enable low-loss and programmable interferometers for manipulating hundreds of spatial modes. Here, we discuss the SOI nanophotonics platform for quantum photonic circuits with hundreds-to-thousands of optical elements and the associated challenges. We compare SOI to competing technologies in terms of requirements for quantum optical systems. We review recent results on large-scale quantum state evolution circuits and strategies for realizing high-fidelity heralded gates with imperfect, practical systems. Next, we review recent results on silicon photonics-based photon-pair sources and device architectures, and we discuss a path towards large-scale source integration. Finally, we review monolithic integration strategies for single-photon detectors and their essential role in on-chip feed forward operations.

Graphene-silicon layered structures on single-crystalline Ir(111) thin films

DOE PAGES

Que, Yande D.; Tao, Jing; Zhang, Yong; ...

2015-01-20

Epitaxial growth of graphene on transition metal crystals, such as Ru,⁽¹⁻³⁾ Ir,⁽⁴⁻⁶⁾ and Ni,⁽⁷⁾ provides large-area, uniform graphene layers with controllable defect density, which is crucial for practical applications in future devices. To decrease the high cost of single-crystalline metal bulks, single-crystalline metal films are strongly suggested as the substrates for epitaxial growth large-scale high-quality graphene.⁽⁸⁻¹⁰⁾ Moreover, in order to weaken the interactions of graphene with its metal host, which may result in a suppression of the intrinsic properties of graphene,⁽¹¹ ¹²⁾ the method of element intercalation of semiconductors at the interface between an epitaxial graphene layer and a transitionmore » metal substrate has been successfully realized.⁽¹³⁻¹⁶⁾« less

On turbulence decay of a shear-thinning fluid

NASA Astrophysics Data System (ADS)

Rahgozar, S.; Rival, D. E.

2017-12-01

An experimental investigation of turbulent flow in a shear-thinning fluid is presented. The experimental flow is a boundary-free, uniformly sheared flow at a relatively high Reynolds number (i.e., Re λmax=275 ), which decays in time. As just one example of decaying turbulence, the experiment can be thought of as a simple model of bulk turbulence in large arteries. The dimensionless parameters used are Reynolds, Strouhal, and Womersley numbers, which have been adapted according to the characteristics of the present experiment. The working fluid is a solution of aqueous 35 ppm xanthan gum, a well-known shear-thinning fluid. The velocity fields are acquired via time-resolved particle image velocimetry in the streamwise/cross-stream and streamwise/spanwise planes. The results show that the presence of xanthan gum not only modifies the turbulent kinetic energy and the dissipation rate but also significantly alters the characteristics of the large-scale eddies.

6th International Conference on Nanomaterials by Severe Plastic Deformation (NanoSPD6)

NASA Astrophysics Data System (ADS)

2014-08-01

''NanoSPD'' means Nano-material by Severe Plastic Deformation (SPD), which is an efficient way to obtain bulk nano-structured materials. During SPD, the microstructure of the material is transformed into a very fine structure consisting of ultra fine grains (UFG) approaching even the nano-scale. SPD is different from classical large strain forming processes in two aspects: 1. The sample undergoes extremely large strains without significant change in its dimensions, 2. In most SPD processes high hydrostatic stress is applied which makes it possible to deform difficult-to-form materials. This conference is part of a series of conferences taking place every third year; the history of NanoSPD conferences began in 1999 in Moscow (Russia), followed by Vienna in 2002 (Austria), Fukuoka in 2005 (Japan), Goslar in 2008 (Germany), Nanjing in 2011 (China), and Metz in 2014 (France). The preface continues in the pdf.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, Zhaodong; Yang, Mengjin; Schulz, Philip

Organic-inorganic perovskite solar cells have attracted tremendous attention because of their remarkably high power conversion efficiencies. To further improve device performance, it is imperative to obtain fundamental understandings on the photo-response and long-term stability down to the microscopic level. Here, we report the quantitative nanoscale photoconductivity imaging on two methylammonium lead triiodide thin films with different efficiencies by light-stimulated microwave impedance microscopy. The microwave signals are largely uniform across grains and grain boundaries, suggesting that microstructures do not lead to strong spatial variations of the intrinsic photo-response. In contrast, the measured photoconductivity and lifetime are strongly affected by bulk propertiesmore » such as the sample crystallinity. As visualized by the spatial evolution of local photoconductivity, the degradation process begins with the disintegration of grains rather than nucleation and propagation from visible boundaries between grains. In conclusion, our findings provide insights to improve the electro-optical properties of perovskite thin films towards large-scale commercialization.« less

How cosmic microwave background correlations at large angles relate to mass autocorrelations in space

NASA Technical Reports Server (NTRS)

Blumenthal, George R.; Johnston, Kathryn V.

1994-01-01

The Sachs-Wolfe effect is known to produce large angular scale fluctuations in the cosmic microwave background radiation (CMBR) due to gravitational potential fluctuations. We show how the angular correlation function of the CMBR can be expressed explicitly in terms of the mass autocorrelation function xi(r) in the universe. We derive analytic expressions for the angular correlation function and its multipole moments in terms of integrals over xi(r) or its second moment, J(sub 3)(r), which does not need to satisfy the sort of integral constraint that xi(r) must. We derive similar expressions for bulk flow velocity in terms of xi and J(sub 3). One interesting result that emerges directly from this analysis is that, for all angles theta, there is a substantial contribution to the correlation function from a wide range of distance r and that radial shape of this contribution does not vary greatly with angle.

Wave functions of symmetry-protected topological phases from conformal field theories

NASA Astrophysics Data System (ADS)

Scaffidi, Thomas; Ringel, Zohar

2016-03-01

We propose a method for analyzing two-dimensional symmetry-protected topological (SPT) wave functions using a correspondence with conformal field theories (CFTs) and integrable lattice models. This method generalizes the CFT approach for the fractional quantum Hall effect wherein the wave-function amplitude is written as a many-operator correlator in the CFT. Adopting a bottom-up approach, we start from various known microscopic wave functions of SPTs with discrete symmetries and show how the CFT description emerges at large scale, thereby revealing a deep connection between group cocycles and critical, sometimes integrable, models. We show that the CFT describing the bulk wave function is often also the one describing the entanglement spectrum, but not always. Using a plasma analogy, we also prove the existence of hidden quasi-long-range order for a large class of SPTs. Finally, we show how response to symmetry fluxes is easily described in terms of the CFT.

Estimating carbon and nitrogen pools in a forest soil: Influence of soil bulk density methods and rock content

Treesearch

Martin F. Jurgensen; Deborah S. Page-Dumroese; Robert E. Brown; Joanne M. Tirocke; Chris A. Miller; James B. Pickens; Min Wang

2017-01-01

Soils with high rock content are common in many US forests, and contain large amounts of stored C. Accurate measurements of soil bulk density and rock content are critical for calculating and assessing changes in both C and nutrient pool size, but bulk density sampling methods have limitations and sources of variability. Therefore, we evaluated the use of small-...

Relevance of cosmic gamma rays to the mass of gas in the galaxy

NASA Technical Reports Server (NTRS)

Bhat, C. L.; Mayer, C. J.; Wolfendale, A. W.

1985-01-01

The bulk of the diffuse gamma-ray flux comes from cosmic ray interactions in the interstellar medium. A knowledge of the large scale spatial distribution of the Galactic gamma-rays and the cosmic rays enables the distribution of the target gas to be examined. An approach of this type is used here to estimate the total mass of the molecular gas in the galaxy. It is shown to be much less than that previously derived, viz., approximately 6 x 10 to the 8th power solar masses within the solar radius as against approximately 3 x 10 to the 9th power based on 2.6 mm CO measurements.

An outlook on microalgal biofuels.

PubMed

Wijffels, René H; Barbosa, Maria J

2010-08-13

Microalgae are considered one of the most promising feedstocks for biofuels. The productivity of these photosynthetic microorganisms in converting carbon dioxide into carbon-rich lipids, only a step or two away from biodiesel, greatly exceeds that of agricultural oleaginous crops, without competing for arable land. Worldwide, research and demonstration programs are being carried out to develop the technology needed to expand algal lipid production from a craft to a major industrial process. Although microalgae are not yet produced at large scale for bulk applications, recent advances-particularly in the methods of systems biology, genetic engineering, and biorefining-present opportunities to develop this process in a sustainable and economical way within the next 10 to 15 years.

In-situ groundwater remediation by selective colloid mobilization

DOEpatents

Seaman, J.C.; Bertch, P.M.

1998-12-08

An in-situ groundwater remediation pump and treat technique is described which is effective for reclamation of aquifers that have been contaminated with a mixed, metal-containing waste, and which promotes selective mobilization of metal oxide colloids with a cationic surfactant, preferably a quaternary alkylammonium surfactant, without significantly reducing formation permeability that often accompanies large-scale colloid dispersion, thus increasing the efficiency of the remediation effort by enhancing the capture of strongly sorbing contaminants associated with the oxide phases. The resulting suspension can be separated from the bulk solution with controlled pH adjustments to destabilize the oxide colloids, and a clear supernatant which results that can be recycled through the injection well without further waste treatment. 3 figs.

In-situ groundwater remediation by selective colloid mobilization

DOEpatents

Seaman, John C.; Bertch, Paul M.

1998-01-01

An in-situ groundwater remediation pump and treat technique effective for reclamation of aquifers that have been contaminated with a mixed, metal-containing waste, which promotes selective mobilization of metal oxide colloids with a cationic surfactant, preferably a quaternary alkylammonium surfactant, without significantly reducing formation permeability that often accompanies large-scale colloid dispersion, thus increasing the efficiency of the remediation effort by enhancing the capture of strongly sorbing contaminants associated with the oxide phases. The resulting suspension can be separated from the bulk solution with controlled pH adjustments to destabilize the oxide colloids, and a clear supernatant which results that can be recycled through the injection well without further waste treatment.

Spatially-and Temporally-Resolved Multi-Parameter Interferometric Rayleigh Scattering System and Method

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel (Inventor); Cutler, Andrew D. (Inventor); Danehy, Paul M. (Inventor)

2015-01-01

A system that simultaneously measures the translational temperature, bulk velocity, and density in gases by collecting, referencing, and analyzing nanosecond time-scale Rayleigh scattered light from molecules is described. A narrow-band pulsed laser source is used to probe two largely separated measurement locations, one of which is used for reference. The elastically scattered photons containing information from both measurement locations are collected at the same time and analyzed spectrally using a planar Fabry-Perot interferometer. A practical means of referencing the measurement of velocity using the laser frequency, and the density and temperature using the information from the reference measurement location maintained at constant properties is provided.

Multiple yielding processes in a colloidal gel under large amplitude oscillatory stress

NASA Astrophysics Data System (ADS)

Gibaud, Thomas; Perge, Christophe; Lindström, Stefan B.; Taberlet, Nicolas; Manneville, Sébastien

Fatigue refers to the changes in material properties caused by repeatedly applied loads. It has been widely studied for, e.g., construction materials, but much less has been done on soft materials. Here, we characterize the fatigue dynamics of a colloidal gel. Fatigue is induced by large amplitude oscillatory stress (LAOStress), and the local displacements of the gel are measured through high-frequency ultrasonic imaging. We show that fatigue eventually leads to rupture and fluidization. We evidence four successive steps associated with these dynamics: (i) the gel first remains solid, (ii) it then slides against the walls, (iii) the bulk of the sample becomes heterogeneous and displays solid-fluid coexistence, and (iv) it is finally fully fluidized. It is possible to homogeneously scale the duration of each step with respect to the stress oscillation amplitude $\\sigma_0$. The data are compatible with both exponential and power-law scalings with $\\sigma_0$, which hints at two possible interpretations in terms of delayed yielding in terms activated processes or of the Basquin law. Surprisingly, we find that the model parameters behave nonmonotonically as we change the oscillation frequency and/or the gel concentration.

Development of Shape Memory Alloys- Challenges and Solutions

NASA Technical Reports Server (NTRS)

Benafan, Othmane

2016-01-01

Shape memory alloys (SMAs) are a unique class of multifunctional materials that have the ability to recover large deformations or generate high stresses in response to thermal, mechanical andor electromagnetic stimuli. These abilities have made them a viable option for actuation systems in aerospace, medical, and automotive applications, amongst others. However, despite many advantages and the fact that SMA actuators have been developed and used for many years, so far they have only found service in a limited range of applications. In order to expand their applications, further developments are needed to increase their reliability and stability and to address processing, testing and qualification needed for large-scale commercial application of SMA actuators. In this seminar, historical inhibitors of SMA applications and current research efforts by NASA Glenn Research Center and collaborators will be discussed. Relationships between fundamental physicalscientific understanding, and the direct transition to engineering and design of mechanisms using these novel materials will be highlighted. Examples will be presented related to targeted alloy development, microstructural control, and bulk-scale testing as a function of stresses, temperatures and harsh environments. The seminar will conclude with a summary of SMA applications under development and current advances.

Soil water sensor response to bulk electrical conductivity

USDA-ARS?s Scientific Manuscript database

Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

Fluid-rock Interactions recorded in Serpentinites subducted to 60-80 km Depth

NASA Astrophysics Data System (ADS)

Peters, D.; John, T.; Scambelluri, M.; Pettke, D. T.

2016-12-01

The HP metamorphic serpentinised peridotites of Erro-Tobbio (ET, Italy) offer a unique possibility to study fluid-rock interactions in subducted ultrabasic rocks that reached 550-650°C at 2-2.5 GPa. They contain metamorphic olivine + Ti-clinohumite in both the serpentinite matrix and veins cutting the rock foliation, interpreted to represent partial serpentinite dehydration fluid pathways [1,2] being variably retrogressed as e.g., indicated by chrysotile/lizardite mesh textures in vein olivine in strongly altered samples. This study aims to constraining the origin of fluid(s) and the scale(s) of fluid-rock interaction based on major to trace element systematics employing detailed bulk rock (nanoparticulate pressed powder pellet LA-ICP-MS [3] and ion chromatography / liquid ICP-MS analysis), and in situ mineral analysis (work in progress). Bulk data show moderate fluid-mobile element (FME) enrichment for Cs, Rb, Ba, Pb, As, and Sb (up to 100 times primitive mantle (PM)), W (1000 PM), and B (10000 PM). Alkali over U ratios of compiled serpentinite data (n ˜ 620) reveal distinctive global FME enrichment trends for MOR vs. forearc (FA) serpentinisation. ET serpentinites fall into the latter, indicating both sediment-equilibrated fluids and the preservation of characteristic FME enrichment patterns in HP serpentinites. Petrography reveals a multiphase evolution of the HP veins including retrograde serpentinisation, whereas serpentinite hosts have remained largely unaffected by retrogression. Comparison of vein vs. wall rock bulk data indicate vein-forming fluids in equilibrium with wall rocks, however, without evidence for external fluid ingress. The preservation of multiple fluid-rock interaction episodes and the lack of external fluid ingress in the ET HP serpentinites indicate near-closed system behaviour throughout subduction and imprint of characteristic fluid signatures onto the mantle. [1] Scambelluri et al. (1995) Geology, 23, 459-462. [2] John et al. (2011) Earth Planet Sci Lett 308, 65-76. [3] Peters and Pettke (2016) GGR, DOI: 10.1111/ggr.12125.

Using an atmospheric boundary layer model to force global ocean models

NASA Astrophysics Data System (ADS)

Abel, Rafael; Böning, Claus

2014-05-01

Current practices in the atmospheric forcing of ocean model simulations can lead to unphysical behaviours. The problem lies in the bulk formulation of the turbulent air-sea fluxes in the conjunction with a prescribed, and unresponsive, atmospheric state (as given by reanalysis products). This can have impacts both on mesoscale processes as well as on the dynamics of the large-scale circulation. First, a possible local mismatch between the given atmospheric state and evolving sea surface temperature (SST) signatures can occur, especially for mesoscale features such as frontal areas, eddies, or near the sea ice edge. Any ocean front shift or evolution of mesoscale anomalies results in excessive, unrealistic surface fluxes due to the lack of atmospheric adaptation. Second, a subtle distortion in the sensitive balance of feedback processes being critical for the thermohaline circulation. Since the bulk formulations assume an infinite atmospheric heat capacity, resulting SST anomalies are strongly damped even on basin-scales (e.g. from trends in the Atlantic meridional overturning circulation). In consequence, an important negative feedback is eliminated, rendering the system excessively susceptible to small anomalies (or errors) in the freshwater fluxes. Previous studies (Seager et al., 1995, J. Clim.) have suggested a partial forcing issue remedy that aimed for a physically more realistic determination of air-sea fluxes by allowing some (thermodynamic) adaptation of the atmospheric boundary layer to SST changes. In this study a modernized formulation of this approach (Deremble et al., 2013, Mon. Weather Rev.; 'CheapAML') is implemented in a global ocean-ice model with moderate resolution (0.5°; ORCA05). In a set of experiments we explore the solution behaviour of this forcing approach (where only the winds are prescribed, while atmospheric temperature and humidity are computed), contrasting it with the solution obtained from the classical bulk formulation with a non-responsive atmosphere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. K. Kushwaha; Pletikosic, I.; Liang, T.

A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons, and be growable as large, high quality bulk single crystals. Here we show that this materials obstacle is overcome by bulk crystals of lightly Sn-doped Bi 1.1Sb 0.9Te 2S grown by the Vertical Bridgeman method.more » We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunneling microscopy, transport studies, X-ray diffraction, and Raman scattering. We present this material as a high quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states.« less

Implications of PCR and ELISA results on the routes of bulk-tank contamination with Mycobacterium avium ssp. paratuberculosis.

PubMed

Beaver, A; Cazer, C L; Ruegg, P L; Gröhn, Y T; Schukken, Y H

2016-02-01

Mycobacterium avium ssp. paratuberculosis (MAP), the etiologic agent of Johne's disease in dairy cattle, may enter the bulk tank via environmental contamination or direct excretion into milk. Traditionally, diagnostics to identify MAP in milk target either MAP antibodies (by ELISA) or the organism itself (by culture or PCR). High ELISA titers may be directly associated with excretion of MAP into milk but only indirectly linked to environmental contamination of the bulk tank. Patterns of bulk-milk ELISA and bulk-milk PCR results could therefore provide insight into the routes of contamination and level of infection or environmental burden. Coupled with questionnaire responses pertaining to management, the results of these diagnostic tests could reveal correlations with herd characteristics or on-farm practices that distinguish herds with high and low environmental bulk-tank MAP contamination. A questionnaire on hygiene, management, and Johne's specific parameters was administered to 292 dairy farms in New York, Oregon, and Wisconsin. Bulk-tank samples were collected from each farm for evaluation by real-time PCR and ELISA. Before DNA extraction and testing of the unknown samples, bulk-milk template preparation was optimized with respect to parameters such as MAP fractionation patterns and lysis. Two regression models were developed to explore the relationships among bulk-tank PCR, ELISA, environmental predictors, and herd characteristics. First, ELISA optical density (OD) was designated as the outcome in a linear regression model. Second, the log odds of being PCR positive in the bulk tank were modeled using binary logistic regression with penalized maximum likelihood. The proportion of PCR-positive bulk tanks was highest for New York and for organic farms, providing a clue as to the geographical patterns of MAP-positive bulk-tank samples and relationship to production type. Bulk-milk PCR positivity was also higher for large relative to small herds. The models revealed that bulk-milk PCR result could predict ELISA OD, with PCR-positive results corresponding to high bulk-milk ELISA titers. Similarly, ELISA was a predictor of PCR result, although the association was stronger for organic farms. Despite agreement between high bulk-milk ELISA titers and positive PCR results, a large proportion of high ELISA farms had PCR-negative bulk tanks, suggesting that farms are able to maintain satisfactory hygiene and management despite a presence of MAP in these herds. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

L1 0 Fe -Pd Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions

NASA Astrophysics Data System (ADS)

Zhang, De-Lin; Sun, Congli; Lv, Yang; Schliep, Karl B.; Zhao, Zhengyang; Chen, Jun-Yang; Voyles, Paul M.; Wang, Jian-Ping

2018-04-01

Magnetic materials that possess large bulk perpendicular magnetic anisotropy (PMA) are essential for the development of magnetic tunnel junctions (MTJs) used in future spintronic memory and logic devices. The addition of an antiferromagnetic layer to these MTJs was recently predicted to facilitate ultrafast magnetization switching. Here, we report a demonstration of a bulk perpendicular synthetic antiferromagnetic (PSAFM) structure comprised of a (001) textured Fe -Pd /Ru /Fe -Pd trilayer with a face-centered-cubic (fcc) phase Ru spacer. The L1 0 Fe -Pd PSAFM structure shows a large bulk PMA (Ku˜10.2 Merg /cm3 ) and strong antiferromagnetic coupling (-JIEC˜2.60 erg /cm2 ). Full perpendicular magnetic tunnel junctions (PMTJs) with a L1 0 Fe -Pd PSAFM layer are then fabricated. Tunneling magnetoresistance ratios of up to approximately 25% (approximately 60%) are observed at room temperature (5 K) after postannealing at 350 °C . Exhibiting high thermal stabilities and large Ku , the bulk PMTJs with an L1 0 Fe -Pd PSAFM layer could pave a way for next-generation ultrahigh-density and ultralow-energy spintronic applications.

Resolving molecular gas to ~500 pc in a unique star forming disk galaxy at z~2

NASA Astrophysics Data System (ADS)

Brisbin, Drew; Aravena, Manuel; Hodge, Jacqueline; Carilli, Chris Luke; Daddi, Emanuele; Dannerbauer, Helmut; Riechers, Dominik; Wagg, Jeff

2018-06-01

We have resolved molecular gas in a 'typical' star forming disk galaxy at z>2 down to the scale of ~500 pc. Previous observations of CO and [CI] lines on larger spatial scales have revealed bulk molecular and atomic gas properties indicating that the target is a massive disk galaxy with large gas reserves. Unlike many galaxies studied at high redshift, it is undergoing modest quiescent star formation rather than bursty centrally concentrated star formation. Therefore this galaxy represents an under-studied, but cosmologically important population in the early universe. Our new observations of CO (4-3) highlight the clumpy molecular gas fuelling star formation throughout the disk. Underlying continuum from cold dust provides a key constraint on star formation rate surface densities, allowing us to examine the star formation rate surface density scaling law in a never-before-tested regime of early universe galaxies.These observations enable an unprecedented view of the obscured star formation that is hidden to optical/UV imaging and trace molecular gas on a fine enough scale to resolve morphological traits and provide a view akin to single dish surveys in the local universe.

A novel HTS magnetic levitation dining table

NASA Astrophysics Data System (ADS)

Lu, Yiyun; Huang, Huiying

2018-05-01

High temperature superconducting (HTS) bulk can levitate above or suspend below a permanent magnet stably. Many magnificent potential applications of HTS bulk are proposed by researchers. Until now, few reports have been found for real applications of HTS bulk. A complete set of small-scale HTS magnetic levitation table is proposed in the paper. The HTS magnetic levitation table includes an annular HTS magnetic levitation system which is composed of an annular HTS bulk array and an annular permanent magnet guideway (PMG). The annular PMG and the annular cryogenics vessel which used to maintain low temperature environment of the HTS bulk array are designed. 62 YBCO bulks are used to locate at the bottom of the annular vessel. A 3D-model finite element numerical method is used to design the HTS bulk magnetic levitation system. Equivalent magnetic levitation and guidance forces calculation rules are proposed aimed at the annular HTS magnetic levitation system stability. Based on the proposed method, levitation and guidance forces curves of the one YBCO bulk magnetic above PMG could be obtained. This method also can use to assist PMG design to check whether the designed PMG could reach the basic demand of the HTS magnetic levitation table.

Nanometre-scale 3D defects in Cr2AlC thin films.

PubMed

Chen, Y T; Music, D; Shang, L; Mayer, J; Schneider, J M

2017-04-20

MAX-phase Cr 2 AlC containing thin films were synthesized by magnetron sputtering in an industrial system. Nanometre-scale 3D defects are observed near the boundary between regions of Cr 2 AlC and of the disordered solid solution (CrAl) x C y . Shrinkage of the Cr-Cr interplanar distance and elongation of the Cr-Al distance in the vicinity of the defects are detected using transmission electron microscopy. The here observed deformation surrounding the defects was described using density functional theory by comparing the DOS of bulk Cr 2 AlC with the DOS of a strained and unstrained Cr 2 AlC(0001) surface. From the partial density of states analysis, it can be learned that Cr-C bonds are stronger than Cr-Al bonds in bulk Cr 2 AlC. Upon Cr 2 AlC(0001) surface formation, both bonds are weakened. While the Cr-C bonds recover their bulk strength as Cr 2 AlC(0001) is strained, the Cr-Al bonds experience only a partial recovery, still being weaker than their bulk counterparts. Hence, the strain induced bond strengthening in Cr 2 AlC(0001) is larger for Cr d - C p bonds than for Cr d - Al p bonds. The here observed changes in bonding due to the formation of a strained surface are consistent with the experimentally observed elongation of the Cr-Al distance in the vicinity of nm-scale 3D defects in Cr 2 AlC thin films.

Influence of crop type specification and spatial resolution on empirical modeling of field-scale Maize and Soybean carbon fluxes in the US Great Plains

NASA Astrophysics Data System (ADS)

McCombs, A. G.; Hiscox, A.; Wang, C.; Desai, A. R.

2016-12-01

A challenge in satellite land surface remote-sensing models of ecosystem carbon dynamics in agricultural systems is the lack of differentiation by crop type and management. This generalization can lead to large discrepancies between model predictions and eddy covariance flux tower observations of net ecosystem exchange of CO2 (NEE). Literature confirms that NEE varies remarkably among different crop types making the generalization of agriculture in remote sensing based models inaccurate. Here, we address this inaccuracy by identifying and mapping net ecosystem exchange (NEE) in agricultural fields by comparing bulk modeling and modeling by crop type, and using this information to develop empirical models for future use. We focus on mapping NEE in maize and soybean fields in the US Great Plains at higher spatial resolution using the fusion of MODIS and LandSAT surface reflectance. MODIS observed reflectance was downscaled using the ESTARFM downscaling methodology to match spatial scales to those found in LandSAT and that are more appropriate for carbon dynamics in agriculture fields. A multiple regression model was developed from surface reflectance of the downscaled MODIS and LandSAT remote sensing values calibrated against five FLUXNET/AMERIFLUX flux towers located on soybean and/or maize agricultural fields in the US Great Plains with multi-year NEE observations. Our new methodology improves upon bulk approximates to map and model carbon dynamics in maize and soybean fields, which have significantly different photosynthetic capacities.

Determination of external and internal mass transfer limitation in nitrifying microbial aggregates.

PubMed

Wilén, Britt-Marie; Gapes, Daniel; Keller, Jürg

2004-05-20

In this article we present a study of the effects of external and internal mass transfer limitation of oxygen in a nitrifying system. The oxygen uptake rates (OUR) were measured on both a macro-scale with a respirometric reactor using off-gas analysis (Titrimetric and Off-Gas Analysis (TOGA) sensor) and on a micro-scale with microsensors. These two methods provide independent, accurate measurements of the reaction rates and concentration profiles around and in the granules. The TOGA sensor and microsensor measurements showed a significant external mass transfer effect at low dissolved oxygen (DO) concentrations in the bulk liquid while it was insignificant at higher DO concentrations. The oxygen distribution with anaerobic or anoxic conditions in the center clearly shows major mass transfer limitation in the aggregate interior. The large drop in DO concentration of 22-80% between the bulk liquid and aggregate surface demonstrates that the external mass transfer resistance is also highly important. The maximum OUR even for floccular biomass was only attained at much higher DO concentrations (approximately 8 mg/L) than typically used in such systems. For granules, the DO required for maximal activity was estimated to be >20 mg/L, clearly indicating the effects of the major external and internal mass transfer limitations on the overall biomass activity. Smaller aggregates had a larger volumetric OUR indicating that the granules may have a lower activity in the interior part of the aggregate. Copyright 2004 Wiley Periodicals, Inc.

Azimuthal diffusion of the large-scale circulation of turbulent Rayleight-Bénard convection

NASA Astrophysics Data System (ADS)

He, Xiaozhou; van Gils, Dennis P. M.; Bodenschatz, Eberhard; Ahlers, Guenter

2015-11-01

We present measurements of the azimuthal orientation θ0 (t) of the large-scale circulation (LSC) of turbulent Rayleight-Bénard convection. The sample was a cylinder with height and diameter equal to 1.12 m. We used compressed SF6 gas at pressures up to 19 bars as the fluid. The measurements covered the Rayleigh-number range 1012 <= Ra <=1014 at a Prandtl number Pr ~= 0 . 80 . We found that the preferred orientation of the LSC upflow was aligned to the West, consistent with Earth's Coriolis force. The LSC azimuthal dynamics was diffusive, driven by the small-scale turbulent fluctuations. For Ra <=1013 the Reynolds number Reθ˙ based on the azimuthal diffusivity had a Ra dependence similar to that seen for 109 <= Ra <=1011 and Pr = 4 . 38 . The Pr dependence Reθ˙ ~Prα with α ~= - 1 . 2 was the same as that found for the Reynolds number based on the root-mean-square fluctuation velocity in the interior bulk flow. For Ra = Ra1* ~= 2 ×1013 Reθ˙ showed the ultimate-state transition and for Ra >= Ra2* ~= 8 ×1013 it had a Ra dependence with an exponent of 0 . 40 +/- 0 . 02 . Supported by the Max Planck Society, the Volkswagenstiftung, the DFD Sonderforschungsbereich SFB963, and NSF Grant DMR11-58514.

Cosmographical Implications

NASA Astrophysics Data System (ADS)

Wright, E. L.

1992-12-01

The COBE() DMR observation of large scale anisotropy of the CMBR allows one to compare the gravitational potential measured using Delta T to the gravitational forces required to produce the observed clustering of galaxies. This comparison helps to define the allowed range of cosmological models. As shown by Wright etal 1992, the COBE Delta T agrees quite well with the bulk flow velocity measured by Bertschinger etal 1990 in a window of radius 6000 km/sec. This is the best evidence that the initial perturbation spectrum in fact followed the Harrison-Zeldovich (and inflationary) prediction that P(k) ~ k(n) with n = 1. Assuming that n ~ 1, one can deduce information about the nature of the matter in the Universe: the first conclusion is that a large amount of non-baryonic dark matter is required. The second conclusion is that a linearly evolving model dominated by Cold Dark Matter produces too little structure on 2500 km/sec scales. However, mixed Cold Plus Hot Dark Matter models, vacuum dominated models, or the Couchman & Carlberg (1992) non-linear recipe for making galaxies out of CDM all seem to reproduce the observed structures on scales from 500-6,000 km/sec while connecting to the COBE results with the expected n ~ 1 slope. () COBE is supported by NASA's Astrophysics Division. Goddard Space Flight Center (GSFC), under the scientific guidance of the COBE Science Working Group, is responsible for the development and operation of COBE.

Depositing bulk or micro-scale electrodes

DOEpatents

Shah, Kedar G.; Pannu, Satinderpall S.; Tolosa, Vanessa; Tooker, Angela C.; Sheth, Heeral J.; Felix, Sarah H.; Delima, Terri L.

2016-11-01

Thicker electrodes are provided on microelectronic device using thermo-compression bonding. A thin-film electrical conducting layer forms electrical conduits and bulk depositing provides an electrode layer on the thin-film electrical conducting layer. An insulating polymer layer encapsulates the electrically thin-film electrical conducting layer and the electrode layer. Some of the insulating layer is removed to expose the electrode layer.

EFFECT OF AERATION BASIN CONFIGURATION ON BULKING AT LOW ORGANIC LOADING

EPA Science Inventory

Continuous-flow laboratory-scale activated sludge units were operated on domestic sewage at low F/M. In CSTR units at the F/M range of 0.05-0.25 g COD removed/g TMLVSS, day, bulking did not occur with a weak (BOD(5) = 139 mg/L) sewage feed and TMLSS = 1.5 g/L. Supplementation of ...

Solar Nebula Magnetohydrodynamic Dynamos: Kinematic Theory, Dynamical Constraints, and Magnetic Transport of Angular Momentum

NASA Technical Reports Server (NTRS)

Stepinski, Tomasz F.; Reyes-Ruiz, Mauricio; Vanhala, Harri A. T.

1993-01-01

A hydromagnetic dynamo provides the best mechanism for contemporaneously producing magnetic fields in a turbulent solar nebula. We investigate the solar nebula in the framework of a steady-state accretion disk model and establish the criteria for a viable nebular dynamo. We have found that typically a magnetic gap exists in the nebula, the region where the degree of ionization is too small for the magnetic field to couple to the gas. The location and width of this gap depend on the particular model; the supposition is that gaps cover different parts of the nebula at different evolutionary stages. We have found, from several dynamical constraints, that the generated magnetic field is likely to saturate at a strength equal to equipartition with the kinetic energy of turbulence. Maxwell stress arising from a large-scale magnetic field may significantly influence nebular structure, and Maxwell stress due to small-scale fields can actually dominate other stresses in the inner parts of the nebula. We also argue that the bulk of nebular gas, within the scale height from the midplane, is stable against Balbus-Hawley instability.

Solution to the problem of the poor cyclic fatigue resistance of bulk metallic glasses

PubMed Central

Launey, Maximilien E.; Hofmann, Douglas C.; Johnson, William L.; Ritchie, Robert O.

2009-01-01

The recent development of metallic glass-matrix composites represents a particular milestone in engineering materials for structural applications owing to their remarkable combination of strength and toughness. However, metallic glasses are highly susceptible to cyclic fatigue damage, and previous attempts to solve this problem have been largely disappointing. Here, we propose and demonstrate a microstructural design strategy to overcome this limitation by matching the microstructural length scales (of the second phase) to mechanical crack-length scales. Specifically, semisolid processing is used to optimize the volume fraction, morphology, and size of second-phase dendrites to confine any initial deformation (shear banding) to the glassy regions separating dendrite arms having length scales of ≈2 μm, i.e., to less than the critical crack size for failure. Confinement of the damage to such interdendritic regions results in enhancement of fatigue lifetimes and increases the fatigue limit by an order of magnitude, making these “designed” composites as resistant to fatigue damage as high-strength steels and aluminum alloys. These design strategies can be universally applied to any other metallic glass systems. PMID:19289820

Mixing characterisation of full-scale membrane bioreactors: CFD modelling with experimental validation.

PubMed

Brannock, M; Wang, Y; Leslie, G

2010-05-01

Membrane Bioreactors (MBRs) have been successfully used in aerobic biological wastewater treatment to solve the perennial problem of effective solids-liquid separation. The optimisation of MBRs requires knowledge of the membrane fouling, biokinetics and mixing. However, research has mainly concentrated on the fouling and biokinetics (Ng and Kim, 2007). Current methods of design for a desired flow regime within MBRs are largely based on assumptions (e.g. complete mixing of tanks) and empirical techniques (e.g. specific mixing energy). However, it is difficult to predict how sludge rheology and vessel design in full-scale installations affects hydrodynamics, hence overall performance. Computational Fluid Dynamics (CFD) provides a method for prediction of how vessel features and mixing energy usage affect the hydrodynamics. In this study, a CFD model was developed which accounts for aeration, sludge rheology and geometry (i.e. bioreactor and membrane module). This MBR CFD model was then applied to two full-scale MBRs and was successfully validated against experimental results. The effect of sludge settling and rheology was found to have a minimal impact on the bulk mixing (i.e. the residence time distribution).

Sn-doped Bi 1.1Sb 0.9Te 2S bulk crystal topological insulator with excellent properties

DOE PAGES

S. K. Kushwaha; Pletikosic, I.; Liang, T.; ...

2016-04-27

A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons, and be growable as large, high quality bulk single crystals. Here we show that this materials obstacle is overcome by bulk crystals of lightly Sn-doped Bi 1.1Sb 0.9Te 2S grown by the Vertical Bridgeman method.more » We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunneling microscopy, transport studies, X-ray diffraction, and Raman scattering. We present this material as a high quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states.« less

The RAPID Toolkit: Facilitating Utility-Scale Renewable Energy Development

Science.gov Websites

energy and bulk transmission projects. The RAPID Toolkit, developed by the National Renewable Energy Renewable Energy Development The RAPID Toolkit: Facilitating Utility-Scale Renewable Energy Development information about federal, state, and local permitting and regulations for utility-scale renewable energy and

New developments in magneto-optical imaging applied to rock magnetism: a case study on meteorites (Invited)

NASA Astrophysics Data System (ADS)

Uehara, M.; Gattacceca, J.; van der Beek, C. J.; Leroux, H.; Jacob, D.

2010-12-01

We present results of an integrated study of metallic grains in meteorites, combining magneto-optical imaging (MOI), petrography, FE-SEM, TEM, and microprobe analyses. Indeed, metallic Fe-Ni grains in meteorites have inner structures due to Ni diffusion during slow cooling subsequent to metamorphism on their parent body. Previous magnetic studies suggested that tetrataenite (ordered FeNi) is the stable magnetic carriers in these meteorites. On the other hand, mineralogical studies showed that tetrataenite is intimately mixed with other Fe-Ni phases (kamacite and taenite, that contain less than 10 wt.% and around 30 wt.% Ni, respectively), and forms complex microstructures (see below). However, due to the typical spatial resolution of classical bulk magnetic measurements (~1 mm), it has been so far difficult to isolate the contribution of these different Fe-Ni minerals. The MOI technique measures the magnetic flux threading a magneto-optically active film directly placed on the sample. This film rotates the polarization direction of transmitted light (Faraday rotation). Through the analyzer of a reflected light microscope, the vertical component of surface magnetic field of the sample is observed with a spatial resolution of a few µm, which allows direct comparison between mineralogical and magnetic microstructures of metal grains. We studied Agen (H5) and Ausson (L5) ordinary chondrites. Optical and electron microscopies showed two types of micron- to submicron-scaled tetrataenite-bearing microstructures: (1) Zoned taenite particles that consist of a taenite core, surrounded by a "cloudy zone" (20-150 nm large tetrataenite granules embedded in taenite matrix), and a 1-10 µm thick tetrataenite rim. (2) Zoneless plessite particles that consist of < 10 µm large tetrataenite grains embedded in a kamacite matrix. MOI of saturation remanence showed that only the nm-sized tetrataenite granules in cloudy zone carry very strong remanence. Micron-scale mapping of coercivity of remanence (Bcr), by means of DC demagnetization coupled with MOI, combined with FE-SEM and TEM study showed that this cloudy zone has zoning in Ni composition, tetrataenite grain size, and Bcr. The center part has finer tetrataenite (20 nm), lower bulk Ni composition (30 wt.%) and higher Bcr values (up to 1 T) than the outer part (150 nm, 55 wt.%, and 400 mT respectively). Therefore, tetrataenite in the cloudy zone is a potential very stable carrier of extraterrestrial remanence. Moreover, magnetically soft minerals (e.g. kamacite) are occasionally inversely magnetized by stray fields from adjacent cloudy zone. This implies that bulk measurements of FeNi-bearing meteorites may be misleading because of microscopic-scale interactions between magnetically hard tetrataenite and other soft minerals.

Summary of Air Force Research Laboratory Support for the NASA Green Propellant Infusion Mission

DTIC Science & Technology

2015-07-01

system to transfer propellant from a bulk propellant tank into a spacecraft tank. It also called for the transfer of propellant from a large transport...launch pressurized propellant tanks on a spacecraft or satellite, a fracture mechanics analysis is required to verify the safe design life of the...a bulk propellant tank into a spacecraft tank. It also called for the transfer of propellant from a large transport container into a specialized

Feasibility of culvert IED detection using thermal neutron activation

NASA Astrophysics Data System (ADS)

Faust, Anthony A.; McFee, John E.; Clifford, Edward T. H.; Andrews, Hugh Robert; Mosquera, Cristian; Roberts, William C.

2012-06-01

Bulk explosives hidden in culverts pose a serious threat to the Canadian and allied armies. Culverts provide an opportunity to conceal insurgent activity, avoid the need for detectable surface disturbances, and limit the applicability of conventional sub-surface sensing techniques. Further, in spite of the large masses of explosives that can be employed, the large sensor{target separation makes detection of the bulk explosive content challeng- ing. Defence R&D Canada { Sueld and Bubble Technology Industries have been developing thermal neutron activation (TNA) sensors for detection of buried bulk explosives for over 15 years. The next generation TNA sensor, known as TNA2, incorporates a number of improvements that allow for increased sensor-to-target dis- tances, making it potentially feasible to detect large improvised explosive devices (IEDs) in culverts using TNA. Experiments to determine the ability of TNA2 to detect improvised explosive devices in culverts are described, and the resulting signal levels observed for relevant quantities of explosives are presented. Observations conrm that bulk explosives detection using TNA against a culvert-IED is possible, with large charges posing a detection challenge at least as dicult as that of a deeply buried anti-tank landmine. Because of the prototype nature of the TNA sensor used, it is not yet possible to make denitive statements about the absolute sensitivity or detection time. Further investigation is warranted.

ROOM TEMPERATURE BULK AND TEMPLATE-FREE SYNTHESIS OF LEUCOEMARLDINE POLYANILINE NANOFIBERS

EPA Science Inventory

An extremely simple single-step method is described for the bulk synthesis of nanofibers of the electronic polymer polyaniline in fully reduced state (leucoemarldine form) without using any reducing agents, surfactants, and/or large amounts of insoluble templates. Chemical oxida...

In vitro culture of large bone substitutes in a new bioreactor: importance of the flow direction.

PubMed

Olivier, V; Hivart, Ph; Descamps, M; Hardouin, P

2007-09-01

New biomaterials combined with osteogenic cells are now being developed as an alternative to autogeneous bone grafts when the skeletal defect reaches a critical size. Yet, the size issue appears to be a key obstacle in the development of bone tissue engineering. Bioreactors are needed to allow the in vitro expansion of cells inside large bulk materials under appropriate conditions. However, no bioreactor has yet been designed for large-scale 3D structures and custom-made scaffolds. In this study, we evaluate the efficiency of a new bioreactor for the in vitro development of large bone substitutes, ensuring the perfusion of large ceramic scaffolds by the nutritive medium. The survival and proliferation of cells inside the scaffolds after 7 and 28 days in this dynamic culture system and the impact of the direction of the flow circulation are evaluated. The follow-up of glucose consumption, DNA quantification and microscopic evaluation all confirmed cell survival and proliferation for a sample under dynamic culture conditions, whereas static culture leads to the death of cells inside the scaffolds. Two directions of flow perfusion were assayed; the convergent direction leads to enhanced results compared to divergent flow.

Confinement and the Glass Transition Temperature in Supported Polymer Films: Molecular Weight, Repeat Unit Modification, and Cooperativity Length Scale Investigations

NASA Astrophysics Data System (ADS)

Mundra, Manish K.

2005-03-01

It is well known that the glass transition temperatures, Tgs, of supported polystyrene (PS) films decrease dramatically with decreasing film thickness below 60-80 nm. However, a detailed understanding of the cause of this effect is lacking. We have investigated the impact of several parameters, including polymer molecular weight (MW), repeat unit structure, and the length scale of cooperatively rearranging regions in bulk. There is no significant effect of PS MW on the Tg-confinement effect over a range of 5,000 to 3,000,000 g/mol. In contrast, the strength of the Tg reduction and the onset of the confinement effect increase dramatically upon changing the polymer from PS to poly(4-tert-butylstyrene) (PTBS), with PTBS exhibiting a Tg reduction relative to bulk at a thickness of 300-400 nm. PTBS also shows a Tg reduction relative to bulk of 47 K in a 21-nm-thick film, more than twice that observed in a PS film of identical thickness. Characterization of the length scale of cooperatively rearranging regions has been done by differential scanning calorimetry but reveals at best a limited correlation with the confinement effect.

Western Wind and Solar Integration Study Phase 3A: Low Levels of Synchronous Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Nicholas W.; Leonardi, Bruno; D'Aquila, Robert

The stability of the North American electric power grids under conditions of high penetrations of wind and solar is a significant concern and possible impediment to reaching renewable energy goals. The 33% wind and solar annual energy penetration considered in this study results in substantial changes to the characteristics of the bulk power system. This includes different power flow patterns, different commitment and dispatch of existing synchronous generation, and different dynamic behavior from wind and solar generation. The Western Wind and Solar Integration Study (WWSIS), sponsored by the U.S. Department of Energy, is one of the largest regional solar andmore » wind integration studies to date. In multiple phases, it has explored different aspects of the question: Can we integrate large amounts of wind and solar energy into the electric power system of the West? The work reported here focused on the impact of low levels of synchronous generation on the transient stability performance in one part of the region in which wind generation has displaced synchronous thermal generation under highly stressed, weak system conditions. It is essentially an extension of WWSIS-3. Transient stability, the ability of the power system to maintain synchronism among all elements following disturbances, is a major constraint on operations in many grids, including the western U.S. and Texas systems. These constraints primarily concern the performance of the large-scale bulk power system. But grid-wide stability concerns with high penetrations of wind and solar are still not thoroughly understood. This work focuses on 'traditional' fundamental frequency stability issues, such as maintaining synchronism, frequency, and voltage. The objectives of this study are to better understand the implications of low levels of synchronous generation and a weak grid on overall system performance by: 1) Investigating the Western Interconnection under conditions of both high renewable generation (e.g., wind and solar) and low synchronous generation (e.g., significant coal power plant decommitment or retirement); and 2) Analyzing both the large-scale stability of the Western Interconnection and regional stability issues driven by more geographically dispersed renewable generation interacting with a transmission grid that evolved with large, central station plants at key nodes. As noted above, the work reported here is an extension of the research performed in WWSIS-3.« less

Large area bulk superconductors

DOEpatents

Miller, Dean J.; Field, Michael B.

2002-01-01

A bulk superconductor having a thickness of not less than about 100 microns is carried by a polycrystalline textured substrate having misorientation angles at the surface thereof not greater than about 15.degree.; the bulk superconductor may have a thickness of not less than about 100 microns and a surface area of not less than about 50 cm.sup.2. The textured substrate may have a thickness not less than about 10 microns and misorientation angles at the surface thereof not greater than about 15.degree.. Also disclosed is a process of manufacturing the bulk superconductor and the polycrystalline biaxially textured substrate material.

Influence of tool speeds on dissimilar friction stir spot welding characteristics of bulk metallic glass/Mg alloy

NASA Astrophysics Data System (ADS)

Shin, Hyung-Seop; Jung, Yoon-Chul; Lee, Jin-Kyu

2012-08-01

A small-scale joining technique of dissimilar friction stir spot welding (FSSW) between bulk metallic glass and Mg alloy sheet has been tried using an apparatus which was devised with a CNC milling machine to give a precise control of tool speeds. The influence of tool speeds on the joining characteristics during FSSW was investigated. As a result, it was found that the rotation speed and plunge speed of a tool during FSSW significantly influenced the welding performance of dissimilar FSSW between bulk metallic glasses and Mg alloy.

Mapping the nanoscale energetic landscape in conductive polymer films with spatially super-resolved exciton dynamics

NASA Astrophysics Data System (ADS)

Ginsberg, Naomi

2015-03-01

The migration of Frenkel excitons, tightly-bound electron-hole pairs, in polymeric organic semiconducting films is critical to the efficiency of bulk heterojunction solar cells. While these materials exhibit a high degree of structural heterogeneity on the nanoscale, traditional measurements of exciton diffusion lengths are performed on bulk samples. Since both the characteristic length scales of structural heterogeneity and the reported bulk diffusion lengths are smaller than the optical diffraction limit, we adapt far-field super-resolution fluorescence imaging to uncover the correlations between the structural and energetic landscapes that the excitons explore.

Acoustic Experiment to Measure the Bulk Viscosity of Near-Critical Xenon in Microgravity

NASA Technical Reports Server (NTRS)

Gillis, K. A.; Shinder, I.; Moldover, M. R.; Zimmerli, G. A.

2002-01-01

We plan a rigorous test of the theory of dynamic scaling by accurately measuring the bulk viscosity of xenon in microgravity 50 times closer to the critical temperature T(sub c) than previous experiments. The bulk viscosity zeta (or "second viscosity" or "dilational viscosity") will be determined by measuring the attenuation length of sound alpha lambda and also measuring the frequency-dependence of the speed of sound. For these measurements, we developed a unique Helmholtz resonator and specialized electro-acoustic transducers. We describe the resonator, the transducers, their performance on Earth, and their expected performance in microgravity.

Development of superconducting magnetic bearing with superconducting coil and bulk superconductor for flywheel energy storage system

NASA Astrophysics Data System (ADS)

Arai, Y.; Seino, H.; Yoshizawa, K.; Nagashima, K.

2013-11-01

We have been developing superconducting magnetic bearing for flywheel energy storage system to be applied to the railway system. The bearing consists of a superconducting coil as a stator and bulk superconductors as a rotor. A flywheel disk connected to the bulk superconductors is suspended contactless by superconducting magnetic bearings (SMBs). We have manufactured a small scale device equipped with the SMB. The flywheel was rotated contactless over 2000 rpm which was a frequency between its rigid body mode and elastic mode. The feasibility of this SMB structure was demonstrated.

The Future of Centrally-Organized Wholesale Electricity Markets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glazer, Craig; Morrison, Jay; Breakman, Paul

The electricity grid in the United States is organized around a network of large, centralized power plants and high voltage transmission lines that transport electricity, sometimes over large distances, before it is delivered to the customer through a local distribution grid. This network of centralized generation and high voltage transmission lines is called the “bulk power system.” Costs relating to bulk power generation typically account for more than half of a customer’s electric bill.1 For this reason, the structure and functioning of wholesale electricity markets have major impacts on costs and economic value for consumers, as well as energy securitymore » and national security. Diverse arrangements for bulk power wholesale markets have evolved over the last several decades. The Southeast and Western United States outside of California have a “bilateral-based” bulk power system where market participants enter into long-term bilateral agreements — using competitive procurements through power marketers, direct arrangements among utilities or with other generation owners, and auctions and exchanges.« less

Crystal nucleation and glass formation in metallic alloy melts

NASA Technical Reports Server (NTRS)

Spaepen, F.

1984-01-01

Homogeneous nucleation, containerless solidification, and bulk formation of metallic glasses are discussed. Homogeneous nucleation is not a limiting factor for metallic glass formation at slow cooling rates if the reduced glass transition temperature is high enough. Such glasses can be made in bulk if heterogeneous nucleants are removed. Containerless processing eleminates potential sources of nucleants, but as drop tube experiments on the Pd-Si alloys show, the free surface may still be a very effective heterogeneous nucleant. Combination of etching and heating in vacuum or fluxing can be effective for cleaning fairly large ingots of nucleants. Reduced gravity processing has a potentially useful role in the fluxing technique, for example to keep large metallic ingots surrounded by a low density, low fluidity flux if this proved difficult under ground conditions. For systems where heterogeneous nucleants in the bulk of the ingot need gravity to segregate to the flux-metal interface, reduced gravity processing may not be appropriate for bulk glass formation.

Theory of Multifarious Quantum Phases and Large Anomalous Hall Effect in Pyrochlore Iridate Thin Films

PubMed Central

Hwang, Kyusung; Kim, Yong Baek

2016-01-01

We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293

The Role of Electrical Anisotropy in Modeling and Interpreting Controlled-Source Electromagnetic Responses for Hydraulic Fracture Monitoring

NASA Astrophysics Data System (ADS)

Trevino, S., III; Hickey, M. S.; Everett, M. E.

2017-12-01

Controlled-Source Electromagnetics (CSEM) can be used to monitor the movement and extent of injection fluid during a hydraulic fracture. The response of the fluid to energization by a CSEM source is dependent upon the electrical conductivity difference between the fluid and background geological formation. An important property that must be taken into account when modeling and interpreting CSEM responses is that electrical conductivity may be anisotropic. We study the effect of electrical anisotropy in both the background formation and the fluid-injection zone. First, various properties of the background formation can affect anisotropy including variations in grain size, composition and bedding-plane orientation. In certain formations, such as shale, the horizontal component of the conductivity can be more than an order of magnitude larger than the vertical component. We study this effect by computing differences in surface CSEM responses using the analytic 1-D anisotropic primary solution of a horizontal electric dipole positioned at the surface. Second, during hydraulic fracturing, the injected fluid can create new fractures and infill existing natural fractures. To include the explicit fracture geometry in modeling, a large increase in the number of nodes and computational time is required which may not be feasible. An alternative is to instead model the large-scale fracture geometry as a uniform slab with an appropriate bulk conductivity. Micro-scale fracture geometry may cause preferential fluid propagation in a single direction or plane which can be represented by electrical anisotropy of the slab. To study such effects of bulk anisotropy on CSEM responses we present results from multiple scenarios of surface to surface hydraulic fracture monitoring using 3-D finite element modeling. The model uses Coulomb-gauged potentials to solve Maxwell's equations in the frequency domain and we have updated the code to allow a triaxial electrical conductivity tensor to be specified. By allowing for formation and target electrical anisotropy these modeling results contribute to a better understanding and faster interpretation of field data.

Milankovitch Modulation of the Ecosystem Dynamics of Fossil Great Lakes

NASA Astrophysics Data System (ADS)

Whiteside, J. H.; Olsen, P. E.; Eglinton, T. I.; Cornet, B.; Huber, P.; McDonald, N. G.

2008-12-01

Triassic and Early Jurassic lacustrine deposits of eastern North American rift basins preserve a spectacular record of precession-related Milankovitch forcing in the Pangean tropics. The abundant and well-preserved fossil fish assemblages from these great lakes demonstrate a sequence of cyclical changes that track the permeating hierarchy of climatic cycles. To detail ecosystem processes correlating with succession of fish communities, we measured bulk δ13Corg through a 100 ky series of Early Jurassic climatic precession-forced lake level cycles in the lower Shuttle Meadow Formation of the Hartford rift basin, CT. The deep-water phase of one of these cycles, the Bluff Head bed, has produced thousands of articulated fish. We observe fluctuations in the bulk δ13Corg of the cyclical strata that reflect differing degrees of lake water stratification, nutrient levels, and relative proportion of algal vs. plant derived organic matter that trace fish community changes. We can exclude extrinsic changes in the global exchangeable reservoirs as an origin of this variability because molecule-level δ13C of n-alkanes of plant leaf waxes from the same strata show no such variability. While at higher taxonomic levels the fish communities responded largely by sorting of taxa by environmental forcing, at the species level the holostean genus Semionotus responded by in situ evolution, and ultimately extinction, of a species flock. Fluctuations at the higher frequency, climatic precessional scale are mirrored at lower frequency, eccentricity modulated, scales, all following the lake-level hierarchical pattern. Thus, lacustrine isotopic ratios amplify the Milankovitch climate signal that was already intensified by sequelae of the end-Triassic extinctions. The degree to which the ecological structure of modern lakes responds to similar environmental cyclicity is largely unknown, but we suspect similar patterns and processes within the Neogene history of the East African great lakes, which may be modified in the future by anthropogenic CO2-driven intensification of the hydrological cycle.

Generic dynamical phase transition in one-dimensional bulk-driven lattice gases with exclusion

NASA Astrophysics Data System (ADS)

Lazarescu, Alexandre

2017-06-01

Dynamical phase transitions are crucial features of the fluctuations of statistical systems, corresponding to boundaries between qualitatively different mechanisms of maintaining unlikely values of dynamical observables over long periods of time. They manifest themselves in the form of non-analyticities in the large deviation function of those observables. In this paper, we look at bulk-driven exclusion processes with open boundaries. It is known that the standard asymmetric simple exclusion process exhibits a dynamical phase transition in the large deviations of the current of particles flowing through it. That phase transition has been described thanks to specific calculation methods relying on the model being exactly solvable, but more general methods have also been used to describe the extreme large deviations of that current, far from the phase transition. We extend those methods to a large class of models based on the ASEP, where we add arbitrary spatial inhomogeneities in the rates and short-range potentials between the particles. We show that, as for the regular ASEP, the large deviation function of the current scales differently with the size of the system if one considers very high or very low currents, pointing to the existence of a dynamical phase transition between those two regimes: high current large deviations are extensive in the system size, and the typical states associated to them are Coulomb gases, which are highly correlated; low current large deviations do not depend on the system size, and the typical states associated to them are anti-shocks, consistently with a hydrodynamic behaviour. Finally, we illustrate our results numerically on a simple example, and we interpret the transition in terms of the current pushing beyond its maximal hydrodynamic value, as well as relate it to the appearance of Tracy-Widom distributions in the relaxation statistics of such models. , which features invited work from the best early-career researchers working within the scope of J. Phys. A. This project is part of the Journal of Physics series’ 50th anniversary celebrations in 2017. Alexandre Lazarescu was selected by the Editorial Board of J. Phys. A as an Emerging Talent.

A Double-Moment Multiple-Phase Four-Class Bulk Ice Scheme. Part II: Simulations of Convective Storms in Different Large-Scale Environments and Comparisons with other Bulk Parameterizations.

NASA Astrophysics Data System (ADS)

Schoenberg Ferrier, Brad; Tao, Wei-Kuo; Simpson, Joanne

1995-04-01

Part I of this study described a detailed four-class bulk ice scheme (4ICE) developed to simulate the hydro-meteor profiles of convective and stratiform precipitation associated with mesoscale convective systems. In Part II, the 4ICE scheme is incorporated into the Goddard Cumulus Ensemble (GCE) model and applied without any `tuning' to two squall lines occurring in widely different environments, namely, one over the `Pica) ocean in the Global Atmospheric Research Program's (GARP) Atlantic Tropical Experiment (GATE) and the other over a midlatitude continent in the Cooperative Huntsville Meteorological Experiment (COHMEX). Comparisons were made both with earlier three-class ice formulations and with observations. In both cases, the 4ICE scheme interacted with the dynamics so as to resemble the observations much more closely than did the model runs with either of the three-class ice parameterizations. The following features were well simulated in the COHMEX case: a lack of stratiform rain at the surface ahead of the storm, reflectivity maxima near 60 dBZ in the vicinity of the melting level, and intense radar echoes up to near the tropopause. These features were in strong contrast with the GATE simulation, which showed extensive trailing stratiform precipitation containing a horizontally oriented radar bright band. Peak reflectivities were below the melting level, rarely exceeding 50 dBz, with a steady decrease in reflectivity with height above. With the other bulk formulations, the large stratiform rain areas were not reproduced in the GATE conditions.The microphysical structure of the model clouds in both environments were more realistic than that of earlier modeling efforts. Number concentrations of ice of O(100 L1) occurred above 6 km in the GATE model clouds as a result of ice enhancement and rime splintering in the 4ICE runs. These processes were more effective in the GATE simulation, because near the freezing level the weaker updrafts were comparable in magnitude to the fall speeds of newly frozen drops. Many of the ice crystals initiated at relatively warm temperatures (above 15°C) grew rapidly by deposition into sizes large enough to be converted to snow. In contrast, in the more intense COHMEX updrafts, very large numbers of small ice crystals were initiated at colder temperatures (below 15°C) by nucleation and stochastic freezing of droplets, such that relatively few ice crystals grew by deposition to sizes large enough to be converted to snow. In addition, the large number of frozen drops of O(5 L1) in the 4ICE run am consistent with airborne microphysical data in intense COHMEX updrafts.Numerous sensitivity experiments were made with the four-class and three-class ice schemes, varying fall speed relationships, particle characteristics, and ice collection efficiencies. These tests provide strong support to the conclusion that the 4ICE scheme gives improved resemblance to observations despite present uncertainties in a number of important microphysical parameters.

A High-Resolution InDel (Insertion–Deletion) Markers-Anchored Consensus Genetic Map Identifies Major QTLs Governing Pod Number and Seed Yield in Chickpea

PubMed Central

Srivastava, Rishi; Singh, Mohar; Bajaj, Deepak; Parida, Swarup K.

2016-01-01

Development and large-scale genotyping of user-friendly informative genome/gene-derived InDel markers in natural and mapping populations is vital for accelerating genomics-assisted breeding applications of chickpea with minimal resource expenses. The present investigation employed a high-throughput whole genome next-generation resequencing strategy in low and high pod number parental accessions and homozygous individuals constituting the bulks from each of two inter-specific mapping populations [(Pusa 1103 × ILWC 46) and (Pusa 256 × ILWC 46)] to develop non-erroneous InDel markers at a genome-wide scale. Comparing these high-quality genomic sequences, 82,360 InDel markers with reference to kabuli genome and 13,891 InDel markers exhibiting differentiation between low and high pod number parental accessions and bulks of aforementioned mapping populations were developed. These informative markers were structurally and functionally annotated in diverse coding and non-coding sequence components of genome/genes of kabuli chickpea. The functional significance of regulatory and coding (frameshift and large-effect mutations) InDel markers for establishing marker-trait linkages through association/genetic mapping was apparent. The markers detected a greater amplification (97%) and intra-specific polymorphic potential (58–87%) among a diverse panel of cultivated desi, kabuli, and wild accessions even by using a simpler cost-efficient agarose gel-based assay implicating their utility in large-scale genetic analysis especially in domesticated chickpea with narrow genetic base. Two high-density inter-specific genetic linkage maps generated using aforesaid mapping populations were integrated to construct a consensus 1479 InDel markers-anchored high-resolution (inter-marker distance: 0.66 cM) genetic map for efficient molecular mapping of major QTLs governing pod number and seed yield per plant in chickpea. Utilizing these high-density genetic maps as anchors, three major genomic regions harboring each of pod number and seed yield robust QTLs (15–28% phenotypic variation explained) were identified on chromosomes 2, 4, and 6. The integration of genetic and physical maps at these QTLs mapped on chromosomes scaled-down the long major QTL intervals into high-resolution short pod number and seed yield robust QTL physical intervals (0.89–2.94 Mb) which were essentially got validated in multiple genetic backgrounds of two chickpea mapping populations. The genome-wide InDel markers including natural allelic variants and genomic loci/genes delineated at major six especially in one colocalized novel congruent robust pod number and seed yield robust QTLs mapped on a high-density consensus genetic map were found most promising in chickpea. These functionally relevant molecular tags can drive marker-assisted genetic enhancement to develop high-yielding cultivars with increased seed/pod number and yield in chickpea. PMID:27695461

Surface and Bulk Nanostructuring of Insulators by Ultrashort Laser Pulses

DTIC Science & Technology

2017-04-05

investigating the non-perturbative scaling of the generated harmonics with the laser field and their bandstructure dependence since recent experimental and...the experimental pro- cedure used to write graphitic electrodes inside diamond bulk by laser irradiation [2–4] for the fabrication of three-dimensional...their bandstructure dependence since recent experimental and theoretical investigations in the literature show that high harmonic generation HHG in wide

Prevalence and Risk Factors of Coxiella burnetii Antibodies in Bulk Milk from Cattle, Sheep, and Goats in Jordan.

PubMed

Obaidat, Mohammad M; Kersh, Gilbert J

2017-04-01

This large-scale cross-sectional study was conducted to determine the prevalence, geographical distribution, and risk factors for the presence of antibodies against Coxiella burnetii in bulk tank milk derived from dairy cattle, sheep, and goats in Jordan. Bulk milk samples were collected from 78 dairy cattle, 48 sheep, and 23 goat farms from various places in Jordan according to the density of these animal species in each region of the country. The samples were tested for C. burnetii antibodies using the CHEKIT Q-Fever Antibody ELISA kit. A standardized questionnaire was also used to collect data from each farm to identify and rank the risk factors for the presence of C. burnetii antibodies. The results revealed that 62.9% (95% confidence interval: 55.1 to 70.0%) of the tested ruminant farms were positive for C. burnetii antibodies. Positive results were obtained from 70.9% (60.6 to 79.5%) of dairy cattle farms, 52.1% (38.3 to 65.5%) of sheep farms, and 56.0% (37.1 to 73.3%) of goat farms. Six factors were associated with the presence of these antibodies on cattle farms, and five factors were associated with these antibodies on sheep and goat farms (chi-square test). The multivariate logistic regression model revealed that large dairy cattle farms, farms that add new animals to the herd, farms that infrequently clean the feeders, and farms in particular areas are 28.6, 19.9, 8.0, and 6.4 times more likely, respectively, to have animals with C. burnetii antibodies. Sheep and goat farms that mix their animals with those from other farms, graze more than 5 km, and infrequently sanitize the feeders were 8.0, 0.06, and 13.6 times more likely, respectively, to have animals with C. burnetii antibodies. These data reveal the widespread exposure of Jordanian ruminants to C. burnetii and suggest a high risk for public health.

Near-surface bulk densities of asteroids derived from dual-polarization radar observations

NASA Astrophysics Data System (ADS)

Virkki, A.; Taylor, P. A.; Zambrano-Marin, L. F.; Howell, E. S.; Nolan, M. C.; Lejoly, C.; Rivera-Valentin, E. G.; Aponte, B. A.

2017-09-01

We present a new method to constrain the near-surface bulk density and surface roughness of regolith on asteroid surfaces using planetary radar measurements. The number of radar observations has increased rapidly during the last five years, allowing us to compare and contrast the radar scattering properties of different small-body populations and compositional types. This provides us with new opportunities to investigate their near-surface physical properties such as the chemical composition, bulk density, porosity, or the structural roughness in the scale of centimeters to meters. Because the radar signal can penetrate into a planetary surface up to a few decimeters, radar can reveal information that is hidden from other ground-based methods, such as optical and infrared measurements. The near-surface structure of asteroids and comets in centimeter-to-meter scale is essential information for robotic and human space missions, impact threat mitigation, and understanding the history of these bodies as well as the formation of the whole Solar System.

Prediction of Material Properties of Nanostructured Polymer Composites Using Atomistic Simulations

NASA Technical Reports Server (NTRS)

Hinkley, J.A.; Clancy, T.C.; Frankland, S.J.V.

2009-01-01

Atomistic models of epoxy polymers were built in order to assess the effect of structure at the nanometer scale on the resulting bulk properties such as elastic modulus and thermal conductivity. Atomistic models of both bulk polymer and carbon nanotube polymer composites were built. For the bulk models, the effect of moisture content and temperature on the resulting elastic constants was calculated. A relatively consistent decrease in modulus was seen with increasing temperature. The dependence of modulus on moisture content was less consistent. This behavior was seen for two different epoxy systems, one containing a difunctional epoxy molecule and the other a tetrafunctional epoxy molecule. Both epoxy structures were crosslinked with diamine curing agents. Multifunctional properties were calculated with the nanocomposite models. Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between the carbon nanotube and the surrounding epoxy matrix. These estimated values were used in a multiscale model in order to predict the thermal conductivity of a nanocomposite as a function of the nanometer scaled molecular structure.

Ultrafast Microwave Welding/Reinforcing Approach at the Interface of Thermoplastic Materials.

PubMed

Poyraz, Selcuk; Zhang, Lin; Schroder, Albrecht; Zhang, Xinyu

2015-10-14

As an attempt to address the needs and tackle the challenges in welding of thermoplastic materials (TPMs), a novel process was performed via short-term microwave (MW) heating of a specific composite, made up of conducting polypyrrole nanogranule (PPy NG) coated carbon and catalyst source precursor (ferrocene) fine particles, at substrate polypropylene (PP) dog bone pieces' interface. Upon vigorous interactions between MWs and electromagnetic absorbent PPy NG coating, the energy was transformed into a large amount of heat leading to a drastic temperature increase that was simultaneously used for the instant carbonization of PPy and the decomposition of fine ferrocene particles, which resulted in multiwalled carbon nanotubes (CNTs) growth at the interface. Meanwhile, the as-grown CNTs on the surface conveyed the heat into the adjacent bulk PP and caused locally molten surface layers' formation. Eventually, the light pressure applied at the interface during the heating process squeezed the molten layers together and a new weld was generated. The method is considerably advantageous compared to other alternatives due to (i) its fast, straightforward, and affordable nature, (ii) its applicability at ambient conditions without the need of any extra equipment or chemicals, and also (iii) its ability to provide clean, durable, and functional welds, via precisely controlling process parameters, without causing any thermal distortion or physical alterations in the bulk TPM. Thus, it is believed that this novel welding process will become much preferable for the manufacturing of next-generation TPM composites in large scale, through short-term MW heating.

Bulk-Heterojunction Organic Solar Cells: Five Core Technologies for Their Commercialization.

PubMed

Kang, Hongkyu; Kim, Geunjin; Kim, Junghwan; Kwon, Sooncheol; Kim, Heejoo; Lee, Kwanghee

2016-09-01

The past two decades of vigorous interdisciplinary approaches has seen tremendous breakthroughs in both scientific and technological developments of bulk-heterojunction organic solar cells (OSCs) based on nanocomposites of π-conjugated organic semiconductors. Because of their unique functionalities, the OSC field is expected to enable innovative photovoltaic applications that can be difficult to achieve using traditional inorganic solar cells: OSCs are printable, portable, wearable, disposable, biocompatible, and attachable to curved surfaces. The ultimate objective of this field is to develop cost-effective, stable, and high-performance photovoltaic modules fabricated on large-area flexible plastic substrates via high-volume/throughput roll-to-roll printing processing and thus achieve the practical implementation of OSCs. Recently, intensive research efforts into the development of organic materials, processing techniques, interface engineering, and device architectures have led to a remarkable improvement in power conversion efficiencies, exceeding 11%, which has finally brought OSCs close to commercialization. Current research interests are expanding from academic to industrial viewpoints to improve device stability and compatibility with large-scale printing processes, which must be addressed to realize viable applications. Here, both academic and industrial issues are reviewed by highlighting historically monumental research results and recent state-of-the-art progress in OSCs. Moreover, perspectives on five core technologies that affect the realization of the practical use of OSCs are presented, including device efficiency, device stability, flexible and transparent electrodes, module designs, and printing techniques. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An improved FIB sample preparation technique for site-specific plan-view specimens: A new cutting geometry.

PubMed

Li, Chen; Habler, Gerlinde; Baldwin, Lisa C; Abart, Rainer

2018-01-01

Focused ion beam (FIB) sample preparation technique in plan-view geometry allows direct correlations of the atomic structure study via transmission electron microscopy with micrometer-scale property measurements. However, one main technical difficulty is that a large amount of material must be removed underneath the specimen. Furthermore, directly monitoring the milling process is difficult unless very large material volumes surrounding the TEM specimen site are removed. In this paper, a new cutting geometry is introduced for FIB lift-out sample preparation with plan-view geometry. Firstly, an "isolated" cuboid shaped specimen is cut out, leaving a "bridge" connecting it with the bulk material. Subsequently the two long sides of the "isolated" cuboid are wedged, forming a triangular prism shape. A micromanipulator needle is used for in-situ transfer of the specimen to a FIB TEM grid, which has been mounted parallel with the specimen surface using a simple custom-made sample slit. Finally, the grid is transferred to the standard FIB grid holder for final thinning with standard procedures. This new cutting geometry provides clear viewing angles for monitoring the milling process, which solves the difficulty of judging whether the specimen has been entirely detached from the bulk material, with the least possible damage to the surrounding materials. With an improved success rate and efficiency, this plan-view FIB lift-out specimen preparation technique should have a wide application for material science. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Tracking sedimentation from the historic A.D. 2011 Mississippi River flood in the deltaic wetlands of Louisiana, USA

USGS Publications Warehouse

Khan, Nicole S.; Horton, Benjamin P.; McKee, Karen L.; Jerolmack, Douglas; Falcini, Federico; Enache, Mihaela D.; Vane, Christopher H.

2013-01-01

Management and restoration of the Mississippi River deltaic plain (southern United States) and associated wetlands require a quantitative understanding of sediment delivery during large flood events, past and present. Here, we investigate the sedimentary fingerprint of the 2011 Mississippi River flood across the Louisiana coast (Atchafalaya Delta, Terrebonne, Barataria, and Mississippi River Delta basins) to assess spatial patterns of sedimentation and to identify key indicators of sediment provenance. The sediment deposited in wetlands during the 2011 flood was distinguished from earlier deposits based on biological characteristics, primarily absence of plant roots and increased presence of centric (planktonic) diatoms indicative of riverine origin. By comparison, the lithological (bulk density, organic matter content, and grain size) and chemical (stable carbon isotopes of bulk organic matter) properties of flood sediments were nearly identical to the underlying deposit. Flood sediment deposition was greatest in wetlands near the Atchafalaya and Mississippi Rivers and accounted for a substantial portion (37% to 85%) of the annual accretion measured at nearby monitoring stations. The amount of sediment delivered to those basins (1.1–1.6 g cm−2) was comparable to that reported previously for hurricane sedimentation along the Louisiana coast (0.8–2.1 g cm−2). Our findings not only provide insight into how large-scale river floods influence wetland sedimentation, they lay the groundwork for identifying previous flood events in the stratigraphic record.

Dynamic Cluster Size Effects on the Glass Transition of Thin Films

NASA Astrophysics Data System (ADS)

Wool, Richard

2013-03-01

During cooling from the melt of amorphous materials, it has been shown experimentally that dynamic rigid clusters form in equilibrium with the liquid and their relaxation behavior determines the kinetic nature of Tg [Stanzione et al, J. Non Cryst Solids 357(2): 311-319 2011]. The fractal clusters of size R ~ 5-60 nm (polystyrene) have relaxation times τ ~ R1.8 (solid-to-liquid). They are analogous to sub critical size embryos during crystallization as the amorphous material tries to crystallize due to the strong intermolecular forces at T < Tm ; they are not related to density fluctuations or surface capillary waves. In free-standing thin films of thickness h, several important events occur: (a) The large clusters with R > h are excluded and the thin films have an average faster relaxation time compared to the bulk; consequently Tg decreases as h decreases. (b) The segmental dynamics at the 1 nm scale are largely not affected by nanoconfinement since Tg is determined only by the cluster dynamics with R >> 1 nm. (c) The mobile layer on the surface of free standing films is due to the presence of smaller clusters on the surface which will disappear with increasing rate of testing. (d) With adhesion to a solid substrate, the surface mobile layer disappears as the surface clusters size grow and the change in Tg is suppressed. (e) Physical aging is controlled by the relaxation of the rigid fractal clusters and in thin films, physical aging will occur more rapidly compared to the bulk. (f) The large effect of molecular weight M on Tg appears to be related to the effect on the cluster size distribution giving smaller clusters and faster relation times with increasing M. These results are in accord with the Twinkling Fractal theory of the glass transition.

Effects of Dissolved Organic Matter Properties on Formation and Composition of Mineral-Organic Co-Precipitates at the Nanometer Scale

NASA Astrophysics Data System (ADS)

Possinger, A. R.; Zachman, M.; Lehmann, J.

2016-12-01

An important, yet largely overlooked case of soil organic carbon (SOC) stabilization through mineral-organic associations is the co-precipitation of dissolved organic matter (DOM) into mineral precipitates as they form. The contribution of co-precipitated DOM to the mineral-stabilized SOC pool is expected to be greatest in soil environments with frequent mineral dissolution and precipitation processes. Compared to surface adsorption, properties of mineral-organic co-precipitates are expected to differ at both the particle scale (e.g., total carbon (C) content and composition) and the molecular scale (e.g., impurities in mineral structure), with potential implications for stability and C turnover; additionally, these properties vary across C sources, amounts, and forms. Consequently, high-resolution visualization and characterization combined with bulk chemical measurements is needed to provide a more complete understanding of co-precipitate formation processes and properties, especially as a function of C co-precipitant characteristics. In this study, we evaluate the effect of model C compound and DOM chemical properties (e.g., iron-binding affinity) on the formation, structure, and chemical properties of ferrihydrite (Fh) (Fe3+3O2 •0.5H2O) co-precipitates. Salicylic acid (SA), sucrose and water-extractable DOM from coniferous or deciduous-dominated organic soils were either adsorbed to pre-formed Fh or co-precipitated with Fh. At a C/Fe ratio 10, the amount of co-precipitated C differed among all organic compounds, and for DOM, was more than 2X greater for co-precipitation than adsorption, suggesting a greater capacity for C retention. To probe the molecular-scale C spatial distribution of Fh-SA particles, we obtained Scanning Transmission Electron Microscopy with Electron Energy Loss Spectroscopy (STEM-EELS) maps at a nanometer-scale spatial pixel resolution. Additionally, we will present chemical characteristics of organic-Fh co-precipitates and adsorption complexes investigated in bulk using C Near-Edge X-ray Absorption Fine Structure (NEXAFS) and Fourier Transform Infrared (FT-IR) spectroscopy. Ultimately, these observations of model co-precipitation systems will be used to better interpret observations of putative co-precipitated OM in natural soils.

Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Sheng; Covino, Timothy P.; Sivapalan, Murugesu

In this paper, we use a dynamic network flow model, coupled with a transient storage zone biogeochemical model, to simulate dissolved nutrient removal processes at the channel network scale. We have explored several scenarios in respect of the combination of rainfall variability, and the biological and geomorphic characteristics of the catchment, to understand the dominant controls on removal and delivery of dissolved nutrients (e.g., nitrate). These model-based theoretical analyses suggested that while nutrient removal efficiency is lower during flood events compared to during baseflow periods, flood events contribute significantly to bulk nutrient removal, whereas bulk removal during baseflow periods ismore » less. This is due to the fact that nutrient supply is larger during flood events; this trend is even stronger in large rivers. However, the efficiency of removal during both periods decreases in larger rivers, however, due to (i) increasing flow velocities and thus decreasing residence time, and (ii) increasing flow depth, and thus decreasing nutrient uptake rates. Besides nutrient removal processes can be divided into two parts: in the main channel and in the hyporheic transient storage zone. When assessing their relative contributions the size of the transient storage zone is a dominant control, followed by uptake rates in the main channel and in the transient storage zone. Increasing size of the transient storage zone with downstream distance affects the relative contributions to nutrient removal of the water column and the transient storage zone, which also impacts the way nutrient removal rates scale with increasing size of rivers. Intra-annual hydrologic variability has a significant impact on removal rates at all scales: the more variable the streamflow is, compared to mean discharge, the less nutrient is removed in the channel network. A scale-independent first order uptake coefficient, ke, estimated from model simulations, is highly dependent on the relative size of the transient storage zone and how it changes in the downstream direction, as well as the nature of hydrologic variability.« less

Processing of Bulk YBa2Cu3O(7-x) High Temperature Superconductor Materials for Gravity Modification Experiments and Performance Under AC Levitation

NASA Technical Reports Server (NTRS)

Koczor, Ronald; Noever, David; Hiser, Robert

1999-01-01

We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of bulk-processed high temperature superconductor disks. Others have indicated that large annular disks (on the order of 25cm diameter) and AC levitation fields play an essential role in their observed experiments. We report experiments in processing such large bulk superconductors. Successful results depend on material mechanical characteristics, and pressure and heat treat protocols. Annular disks having rough dimensions of 30cm O.D., 7cm I.D. and 1 cm thickness have been routinely fabricated and tested under AC levitation fields ranging from 45 to 300OHz. Implications for space transportation initiatives and power storage flywheel technology will be discussed.

Large-scale filaments associated with Milky Way spiral arms

NASA Astrophysics Data System (ADS)

Wang, Ke; Testi, Leonardo; Ginsburg, Adam; Walmsley, C. Malcolm; Molinari, Sergio; Schisano, Eugenio

2015-07-01

The ubiquity of filamentary structure at various scales throughout the Galaxy has triggered a renewed interest in their formation, evolution, and role in star formation. The largest filaments can reach up to Galactic scale as part of the spiral arm structure. However, such large-scale filaments are hard to identify systematically due to limitations in identifying methodology (i.e. as extinction features). We present a new approach to directly search for the largest, coldest, and densest filaments in the Galaxy, making use of sensitive Herschel Hi-GAL (Herschel Infrared Galactic Plane Survey) data complemented by spectral line cubes. We present a sample of the nine most prominent Herschel filaments, including six identified from a pilot search field plus three from outside the field. These filaments measure 37-99 pc long and 0.6-3.0 pc wide with masses (0.5-8.3) × 104 M⊙, and beam-averaged (28 arcsec, or 0.4-0.7 pc) peak H2 column densities of (1.7-9.3)× 1022 cm- 2. The bulk of the filaments are relatively cold (17-21 K), while some local clumps have a dust temperature up to 25-47 K. All the filaments are located within ≲60 pc from the Galactic mid-plane. Comparing the filaments to a recent spiral arm model incorporating the latest parallax measurements, we find that 7/9 of them reside within arms, but most are close to arm edges. These filaments are comparable in length to the Galactic scaleheight and therefore are not simply part of a grander turbulent cascade.

An efficient top-down approach for the fabrication of large-aspect-ratio g-C3N4 nanosheets with enhanced photocatalytic activities.

PubMed

Tong, Jincheng; Zhang, Li; Li, Fei; Li, Mingming; Cao, Shaokui

2015-09-28

Graphitic carbon nitride (g-C3N4) nanosheets with large aspect ratios were fabricated from bulk g-C3N4 through an efficient top-down approach of moderate disintegration-exfoliation using diluted H2SO4 as an "efficient knife". By prior disintegration in a diluted H2SO4 solution, the exfoliation of bulk g-C3N4 was effectively accelerated. The as-prepared g-C3N4 nanosheets possess a two-dimensional (2D) thin-layer structure with seven-atom thickness, a large lateral size of about 1 μm, and a high specific surface area of 80 m(2) g(-1). Compared with the bulk precursor, the g-C3N4 nanosheets showed much higher efficiency of photogenerated charge transfer and separation, and consequently exhibited enhanced photocatalytic activity toward hydrogen evolution and pollutant decomposition under both full-sunlight and visible-light irradiation.

Oligosaccharide/silicon-containing block copolymers with 5 nm features for lithographic applications.

PubMed

Cushen, Julia D; Otsuka, Issei; Bates, Christopher M; Halila, Sami; Fort, Sébastien; Rochas, Cyrille; Easley, Jeffrey A; Rausch, Erica L; Thio, Anthony; Borsali, Redouane; Willson, C Grant; Ellison, Christopher J

2012-04-24

Block copolymers demonstrate potential for use in next-generation lithography due to their ability to self-assemble into well-ordered periodic arrays on the 3-100 nm length scale. The successful lithographic application of block copolymers relies on three critical conditions being met: high Flory-Huggins interaction parameters (χ), which enable formation of <10 nm features, etch selectivity between blocks for facile pattern transfer, and thin film self-assembly control. The present paper describes the synthesis and self-assembly of block copolymers composed of naturally derived oligosaccharides coupled to a silicon-containing polystyrene derivative synthesized by activators regenerated by electron transfer atom transfer radical polymerization. The block copolymers have a large χ and a low degree of polymerization (N) enabling formation of 5 nm feature diameters, incorporate silicon in one block for oxygen reactive ion etch contrast, and exhibit bulk and thin film self-assembly of hexagonally packed cylinders facilitated by a combination of spin coating and solvent annealing techniques. As observed by small angle X-ray scattering and atomic force microscopy, these materials exhibit some of the smallest block copolymer features in the bulk and in thin films reported to date.

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

DOE PAGES

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.; ...

2016-07-08

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain,more » texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. Additionally, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.« less

A kinetic Monte Carlo approach to diffusion-controlled thermal desorption spectroscopy

NASA Astrophysics Data System (ADS)

Schablitzki, T.; Rogal, J.; Drautz, R.

2017-06-01

Atomistic simulations of thermal desorption spectra for effusion from bulk materials to characterize binding or trapping sites are a challenging task as large system sizes as well as extended time scales are required. Here, we introduce an approach where we combine kinetic Monte Carlo with an analytic approximation of the superbasins within the framework of absorbing Markov chains. We apply our approach to the effusion of hydrogen from BCC iron, where the diffusion within bulk grains is coarse grained using absorbing Markov chains, which provide an exact solution of the dynamics within a superbasin. Our analytic approximation to the superbasin is transferable with respect to grain size and elliptical shapes and can be applied in simulations with constant temperature as well as constant heating rate. The resulting thermal desorption spectra are in close agreement with direct kinetic Monte Carlo simulations, but the calculations are computationally much more efficient. Our approach is thus applicable to much larger system sizes and provides a first step towards an atomistic understanding of the influence of structural features on the position and shape of peaks in thermal desorption spectra. This article is part of the themed issue 'The challenges of hydrogen and metals'.

Natural convection along a heated vertical plate immersed in a nonlinearly stratified medium: application to liquefied gas storage

NASA Astrophysics Data System (ADS)

Forestier, M.; Haldenwang, P.

We consider free convection driven by a heated vertical plate immersed in a nonlinearly stratified medium. The plate supplies a uniform horizontal heat flux to a fluid, the bulk of which has a stable stratification, characterized by a non-uniform vertical temperature gradient. This gradient is assumed to have a typical length scale of variation, denoted Z0, while 0, and the physical properties of the medium.We then apply the new theory to the natural convection affecting the vapour phase in a liquefied pure gas tank (e.g. the cryogenic storage of hydrogen). It is assumed that the cylindrical storage tank is subject to a constant uniform heat flux on its lateral and top walls. We are interested in the vapour motion above a residual layer of liquid in equilibrium with the vapour. High-precision axisymmetric numerical computations show that the flow remains steady for a large range of parameters, and that a bulk stratification characterized by a quadratic temperature profile is undoubtedly present. The application of the theory permits a comparison of the numerical and analytic results, showing that the theory satisfactorily predicts the primary dynamical and thermal properties of the storage tank.

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy.

PubMed

Tremsin, Anton S; Gao, Yan; Dial, Laura C; Grazzi, Francesco; Shinohara, Takenao

2016-01-01

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain, texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. In addition, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.

Quantitative description on structure–property relationships of Li-ion battery materials for high-throughput computations

PubMed Central

Wang, Youwei; Zhang, Wenqing; Chen, Lidong; Shi, Siqi; Liu, Jianjun

2017-01-01

Abstract Li-ion batteries are a key technology for addressing the global challenge of clean renewable energy and environment pollution. Their contemporary applications, for portable electronic devices, electric vehicles, and large-scale power grids, stimulate the development of high-performance battery materials with high energy density, high power, good safety, and long lifetime. High-throughput calculations provide a practical strategy to discover new battery materials and optimize currently known material performances. Most cathode materials screened by the previous high-throughput calculations cannot meet the requirement of practical applications because only capacity, voltage and volume change of bulk were considered. It is important to include more structure–property relationships, such as point defects, surface and interface, doping and metal-mixture and nanosize effects, in high-throughput calculations. In this review, we established quantitative description of structure–property relationships in Li-ion battery materials by the intrinsic bulk parameters, which can be applied in future high-throughput calculations to screen Li-ion battery materials. Based on these parameterized structure–property relationships, a possible high-throughput computational screening flow path is proposed to obtain high-performance battery materials. PMID:28458737

Indoor seismology by probing the Earth's interior by using sound velocity measurements at high pressures and temperatures.

PubMed

Li, Baosheng; Liebermann, Robert C

2007-05-29

The adiabatic bulk (K(S)) and shear (G) moduli of mantle materials at high pressure and temperature can be obtained directly by measuring compressional and shear wave velocities in the laboratory with experimental techniques based on physical acoustics. We present the application of the current state-of-the-art experimental techniques by using ultrasonic interferometry in conjunction with synchrotron x radiation to study the elasticity of olivine and pyroxenes and their high-pressure phases. By using these updated thermoelasticity data for these phases, velocity and density profiles for a pyrolite model are constructed and compared with radial seismic models. We conclude that pyrolite provides an adequate explanation of the major seismic discontinuities at 410- and 660-km depths, the gradient in the transition zone, as well as the velocities in the lower mantle, if the uncertainties in the modeling and the variations in different seismic models are considered. The characteristics of the seismic scaling factors in response to thermal anomalies suggest that anticorrelations between bulk sound and shear wave velocities, as well as the large positive density anomalies observed in the lower mantle, cannot be explained fully without invoking chemical variations.

The behavior of vapor bubbles during boiling enhanced with acoustics and open microchannels

NASA Astrophysics Data System (ADS)

Boziuk, Thomas; Smith, Marc K.; Glezer, Ari

2012-11-01

Boiling heat transfer on a submerged heated surface is enhanced by combining a grid of surface micromachined open channels and ultrasonic acoustic actuation to control the formation and evolution of vapor bubbles and to inhibit the instability that leads to film boiling at the critical heat flux (CHF). The microchannels provide nucleation sites for vapor bubble formation and enable the entrainment of bulk subcooled fluid to these sites for sustained evaporation. Acoustic actuation excites interfacial oscillations of the detached bubbles and leads to accelerated condensation in the bulk fluid, thereby limiting the formation of vapor columns that precede the CHF instability. The combined effects of microchannels and acoustic actuation are investigated experimentally with emphasis on bubble nucleation, growth, detachment, and condensation. It is shown that this hybrid approach leads to a significant increase in the critical heat flux, a reduction of the vapor mass above the surface, and the breakup of low-frequency vapor slug formation. A large-scale model of the microchannel grid reveals details of the flow near the nucleation site and shows that the presence of the microchannels decreases the surface superheat at a given heat flux. Supported by ONR.

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

NASA Astrophysics Data System (ADS)

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.; Grazzi, Francesco; Shinohara, Takenao

2016-01-01

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with 100 μm resolution) distribution of some microstructure properties, such as residual strain, texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. In addition, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain,more » texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. Additionally, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.« less

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

PubMed Central

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.; Grazzi, Francesco; Shinohara, Takenao

2016-01-01

Abstract Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain, texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. In addition, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components. PMID:27877885

Flow of ultra-hot Precambrian orogens and the making of crustal layering in Phanerozoic orogenic plateaux

NASA Astrophysics Data System (ADS)

Chardon, Dominique; Gapais, Denis; Cagnard, Florence; Jayananda, Mudlappa; Peucat, Jean-Jacques

2010-05-01

Reassessment of structural / metamorphic properties of ultra-hot Precambrian orogens and shortening of model weak lithospheres support a syn-convergence flow mode on an orogen scale, with a large component of horizontal finite elongation parallel to the orogen. This orogen-scale flow mode combines distributed shortening, gravity-driven flow, lateral escape, and three-dimensional mass redistribution of buried supracrustal rocks, magmas and migmatites in a thick fluid lower crust. This combination preserves a nearly flat surface and Moho. The upper crust maintains a nearly constant thickness by real-time erosion and near-field clastic sedimentation and by ablation at its base by burial of pop-downs into the lower crust. Steady state regime of these orogens is allowed by activation of an attachment layer that maintains kinematic compatibility between the thin and dominantly plastic upper crust and a thick "water bed" of lower crust. Because very thin lithospheres of orogenic plateaux and Precambrian hot orogens have similar thermomechanical structures, bulk orogenic flow comparable to that governing Precambrian hot orogens should actually operate through today's orogenic plateaux as well. Thus, syn-convergence flow fabrics documented on exposed crustal sections of ancient hot orogens that have not undergone collapse may be used to infer the nature of flow fabrics that are imaged by geophysical techniques beneath orogenic plateaux. We provide a detailed geological perspective on syn-convergence crustal flow in relation to magma emplacement and partial melting on a wide oblique crustal transition of the Neoarchean ultra-hot orogen of Southern India. We document sub-horizontal bulk longitudinal flow of the partially molten lower crust over a protracted period of 60 Ma. Bulk flow results from the interplay of (1) pervasive longitudinal transtensional flow of the partially molten crust, (2) longitudinal coaxial flow on flat fabrics in early plutons, (3) distributed, orogen-normal shortening, (4) emplacement of late prolate shape plutons in the direction of flow, and (5) late, conjugate strike-slip shearing. The macroscopic- to regional scale tectonoplutonic pattern produced by longitudinal flow forms a flat composite anisotropy throughout the lower crust. In the light of GPS data, these results suggest that bulk longitudinal flow accounts for observed deformation of the Tibetan plateau as well as for its seismic structure. This flow mode may be preferred to lateral, east-directed channel flow because it combines both lateral gravity-driven thinning and distributed, orogen-normal shortening of the crust. These results further suggest that lower crustal seismic reflectivity in orogenic belts may not necessarily images fabrics produced by extensional tectonics, as commonly thought, but crustal layering produced by syn-convergence lateral flow.

Compression and Instrumented Indentation Measurements on Biomimetic Polymers

DTIC Science & Technology

2006-09-01

styrene- isoprene triblock copolymer gels are tested and compared using both macro-scale and micro-scale measurements. A methodology is presented to...at stress states and strain rates not available to bulk measurement equipment. In this work, a ballistic gelatin and two styrene- isoprene triblock

GREEN APPROACH TO BULK AND TEMPLATE-FREE SYNTHESIS OF THERMALLY STABLE REDUCED POLYANILINE NANOFIBERS FOR CAPACITOR APPLICATIONS

EPA Science Inventory

An extremely simple green approach is described that generates bulk quantities of nanofibers of the electronic polymer polyaniline in fully reduced state (leucoemeraldine form) in one step without using any reducing agent, surfactants, and/or large amounts of insoluble templates....

BULK AND TEMPLATE-FREE SYNTHESIS OF SILVER NANOWIRES USING CAFFEINE AT ROOM TEMPERATURE

EPA Science Inventory

A simple eco-friendly one-pot method is described to synthesize bulk quantities of nanowires of silver (Ag) using caffeine without the need of reducing agent, surfactants, and/or large amounts of insoluble templates. Chemical reduction of silver salts with caffeine dramatically c...

Atomic-scale bonding of bulk metallic glass to crystalline aluminum

NASA Astrophysics Data System (ADS)

Liu, K. X.; Liu, W. D.; Wang, J. T.; Yan, H. H.; Li, X. J.; Huang, Y. J.; Wei, X. S.; Shen, J.

2008-08-01

A Ti40Zr25Cu12Ni3Be20 bulk metallic glass (BMG) was welded to a crystalline aluminum by the parallel plate explosive welding method. Experimental evidence and numerical simulation show that atomic-scale bonding between the BMG and the crystalline aluminum can be achieved, and the weldment on the BMG side can retain its amorphous state without any indication of crystallization in the welding process. Nanoindentation tests reveal that the interface of the explosive joints exhibits a significant increase in hardness compared to the matrix on its two sides. The joining of BMG and crystalline materials opens a window to the applications of BMGs in engineering.

Hyperscaling-violating Lifshitz hydrodynamics from black-holes: part II

NASA Astrophysics Data System (ADS)

Kiritsis, Elias; Matsuo, Yoshinori

2017-03-01

The derivation of Lifshitz-invariant hydrodynamics from holography, presented in [1] is generalized to arbitrary hyperscaling violating Lifshitz scaling theories with an unbroken U(1) symmetry. The hydrodynamics emerging is non-relativistic with scalar "forcing". By a redefinition of the pressure it becomes standard non-relativistic hydrodynamics in the presence of specific chemical potential for the mass current. The hydrodynamics is compatible with the scaling theory of Lifshitz invariance with hyperscaling violation. The bulk viscosity vanishes while the shear viscosity to entropy ratio is the same as in the relativistic case. We also consider the dimensional reduction ansatz for the hydrodynamics and clarify the difference with previous results suggesting a non-vanishing bulk viscosity.

Localized diffusive motion on two different time scales in solid alkane nanoparticles

NASA Astrophysics Data System (ADS)

Wang, S.-K.; Mamontov, E.; Bai, M.; Hansen, F. Y.; Taub, H.; Copley, J. R. D.; García Sakai, V.; Gasparovic, G.; Jenkins, T.; Tyagi, M.; Herwig, K. W.; Neumann, D. A.; Montfrooij, W.; Volkmann, U. G.

2010-09-01

High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nano- to bulk-sized particles of the alkane n-C32H66. The crystalline-to-plastic and plastic-to-fluid phase transition temperatures are observed to decrease as the particle size decreases. In all samples, localized molecular diffusive motion in the plastic phase occurs on two different time scales: a "fast" motion corresponding to uniaxial rotation about the long molecular axis; and a "slow" motion attributed to conformational changes of the molecule. Contrary to the conventional interpretation in bulk alkanes, the fast uniaxial rotation begins in the low-temperature crystalline phase.

Interfacial Characteristics of Efficient Bulk Heterojunction Solar Cells Fabricated on MoOx Anode Interlayers.

PubMed

Jasieniak, Jacek J; Treat, Neil D; McNeill, Christopher R; de Villers, Bertrand J Tremolet; Della Gaspera, Enrico; Chabinyc, Michael L

2016-05-01

The role of the interface between an MoOx anode interlayer and a polymer:fullerene bulk heterojunction is investigated. Processing differences in the MoOx induce large variations in the vertical stratification of the bulk heterojunction films. These variations are found to be inconsistent in predicting device performance, with a much better gauge being the quantity of polymer chemisorbed to the anode interlayer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exclusion Process with Slow Boundary

NASA Astrophysics Data System (ADS)

Baldasso, Rangel; Menezes, Otávio; Neumann, Adriana; Souza, Rafael R.

2017-06-01

We study the hydrodynamic and the hydrostatic behavior of the simple symmetric exclusion process with slow boundary. The term slow boundary means that particles can be born or die at the boundary sites, at a rate proportional to N^{-θ }, where θ > 0 and N is the scaling parameter. In the bulk, the particles exchange rate is equal to 1. In the hydrostatic scenario, we obtain three different linear profiles, depending on the value of the parameter θ ; in the hydrodynamic scenario, we obtain that the time evolution of the spatial density of particles, in the diffusive scaling, is given by the weak solution of the heat equation, with boundary conditions that depend on θ . If θ \\in (0,1), we get Dirichlet boundary conditions, (which is the same behavior if θ =0, see Farfán in Hydrostatics, statical and dynamical large deviations of boundary driven gradient symmetric exclusion processes, 2008); if θ =1, we get Robin boundary conditions; and, if θ \\in (1,∞), we get Neumann boundary conditions.

Constraints on the extremely high-energy cosmic ray accelerators from classical electrodynamics

NASA Astrophysics Data System (ADS)

Aharonian, F. A.; Belyanin, A. A.; Derishev, E. V.; Kocharovsky, V. V.; Kocharovsky, Vl. V.

2002-07-01

We formulate the general requirements, set by classical electrodynamics, on the sources of extremely high-energy cosmic rays (EHECRs). It is shown that the parameters of EHECR accelerators are strongly limited not only by the particle confinement in large-scale magnetic fields or by the difference in electric potentials (generalized Hillas criterion) but also by the synchrotron radiation, the electro-bremsstrahlung, or the curvature radiation of accelerated particles. Optimization of these requirements in terms of an accelerator's size and magnetic field strength results in the ultimate lower limit to the overall source energy budget, which scales as the fifth power of attainable particle energy. Hard γ rays accompanying generation of EHECRs can be used to probe potential acceleration sites. We apply the results to several populations of astrophysical objects-potential EHECR sources-and discuss their ability to accelerate protons to 1020 eV and beyond. The possibility of gain from ultrarelativistic bulk flows is addressed, with active galactic nuclei and gamma-ray bursts being the examples.

Constraints on the extremely high-energy cosmic rays accelerators from classical electrodynamics

NASA Astrophysics Data System (ADS)

Belyanin, A.; Aharonian, F.; Derishev, E.; Kocharovsky, V.; Kocharovsky, V.

We formulate the general requirements, set by classical electrodynamics, to the sources of extremely high-energy cosmic rays (EHECRs). It is shown that the parameters of EHECR accelerators are strongly limited not only by the particle confinement in large-scale magnetic field or by the difference in electric potentials (generalized Hillas criterion), but also by the synchrotron radiation, the electro-bremsstrahlung, or the curvature radiation of accelerated particles. Optimization of these requirements in terms of accelerator's size and magnetic field strength results in the ultimate lower limit to the overall source energy budget, which scales as the fifth power of attainable particle energy. Hard gamma-rays accompanying generation of EHECRs can be used to probe potential acceleration sites. We apply the results to several populations of astrophysical objects - potential EHECR sources - and discuss their ability to accelerate protons to 1020 eV and beyond. A possibility to gain from ultrarelativistic bulk flows is addressed, with Active Galactic Nuclei and Gamma-Ray Bursts being the examples.

Effect of interfaces on the nearby Brownian motion

PubMed Central

Huang, Kai; Szlufarska, Izabela

2015-01-01

Near-boundary Brownian motion is a classic hydrodynamic problem of great importance in a variety of fields, from biophysics to micro-/nanofluidics. However, owing to challenges in experimental measurements of near-boundary dynamics, the effect of interfaces on Brownian motion has remained elusive. Here we report a computational study of this effect using μs-long large-scale molecular dynamics simulations and our newly developed Green–Kubo relation for friction at the liquid–solid interface. Our computer experiment unambiguously reveals that the t−3/2 long-time decay of the velocity autocorrelation function of a Brownian particle in bulk liquid is replaced by a t−5/2 decay near a boundary. We discover a general breakdown of traditional no-slip boundary condition at short time scales and we show that this breakdown has a profound impact on the near-boundary Brownian motion. Our results demonstrate the potential of Brownian-particle-based micro-/nanosonar to probe the local wettability of liquid–solid interfaces. PMID:26438034

Regional Differences in Tropical Lightning Distributions.

NASA Astrophysics Data System (ADS)

Boccippio, Dennis J.; Goodman, Steven J.; Heckman, Stan

2000-12-01

Observations from the National Aeronautics and Space Administration Optical Transient Detector (OTD) and Tropical Rainfall Measuring Mission (TRMM)-based Lightning Imaging Sensor (LIS) are analyzed for variability between land and ocean, various geographic regions, and different (objectively defined) convective `regimes.' The bulk of the order-of-magnitude differences between land and ocean regional flash rates are accounted for by differences in storm spacing (density) and/or frequency of occurrence, rather than differences in storm instantaneous flash rates, which only vary by a factor of 2 on average. Regional variability in cell density and cell flash rates closely tracks differences in 85-GHz microwave brightness temperatures. Monotonic relationships are found with the gross moist stability of the tropical atmosphere, a large-scale `adjusted state' parameter. This result strongly suggests that it will be possible, using TRMM observations, to objectively test numerical or theoretical predictions of how mesoscale convective organization interacts with the larger-scale environment. Further parameters are suggested for a complete objective definition of tropical convective regimes.

New Composite Thermoelectric Materials for Macro-size Applications

ScienceCinema

Dresselhaus, Mildred [MIT, Cambridge, Massachusetts, United States

2017-12-09

A review will be given of several important recent advances in both thermoelectrics research and industrial thermoelectric applications, which have attracted much attention, increasing incentives for developing advanced materials appropriate for large-scale applications of thermoelectric devices. One promising strategy is the development of materials with a dense packing of random nanostructures as a route for the sacle-up of thermoelectrics applications. The concepts involved in designing composite materials containing nanostructures for thermoelectric applications will be discussed in general terms. Specific application is made to the Bi{sub 2}Te{sub 3} nanocomposite system for use in power generation. Also emphasized are the scientific advantages of the nanocomposite approach for the simultaneous increase in the power factor and decrease of the thermal conductivity, along with the practical advantages of having bulk samples for property measurements and device applications. A straightforward path is identified for the scale-up of thermoelectric materials synthesis containing nanostructured constituents for use in thermoelectric applications. We end with some vision of where the field of thermoelectrics is now heading.

Heterogeneous shear elasticity of glasses: the origin of the boson peak.

PubMed

Marruzzo, Alessia; Schirmacher, Walter; Fratalocchi, Andrea; Ruocco, Giancarlo

2013-01-01

The local elasticity of glasses is known to be inhomogeneous on a microscopic scale compared to that of crystalline materials. Their vibrational spectrum strongly deviates from that expected from Debye's elasticity theory: The density of states deviates from Debye's law, the sound velocity shows a negative dispersion in the boson-peak frequency regime and there is a strong increase of the sound attenuation near the boson-peak frequency. By comparing a mean-field theory of shear-elastic heterogeneity with a large-scale simulation of a soft-sphere glass we demonstrate that the observed anomalies in glasses are caused by elastic heterogeneity. By observing that the macroscopic bulk modulus is frequency independent we show that the boson-peak-related vibrational anomalies are predominantly due to the spatially fluctuating microscopic shear stresses. It is demonstrated that the boson-peak arises from the steep increase of the sound attenuation at a frequency which marks the transition from wave-like excitations to disorder-dominated ones.

Effect of interfaces on the nearby Brownian motion.

PubMed

Huang, Kai; Szlufarska, Izabela

2015-10-06

Near-boundary Brownian motion is a classic hydrodynamic problem of great importance in a variety of fields, from biophysics to micro-/nanofluidics. However, owing to challenges in experimental measurements of near-boundary dynamics, the effect of interfaces on Brownian motion has remained elusive. Here we report a computational study of this effect using μs-long large-scale molecular dynamics simulations and our newly developed Green-Kubo relation for friction at the liquid-solid interface. Our computer experiment unambiguously reveals that the t(-3/2) long-time decay of the velocity autocorrelation function of a Brownian particle in bulk liquid is replaced by a t(-5/2) decay near a boundary. We discover a general breakdown of traditional no-slip boundary condition at short time scales and we show that this breakdown has a profound impact on the near-boundary Brownian motion. Our results demonstrate the potential of Brownian-particle-based micro-/nanosonar to probe the local wettability of liquid-solid interfaces.

Engineered Living Materials: Prospects and Challenges for Using Biological Systems to Direct the Assembly of Smart Materials.

PubMed

Nguyen, Peter Q; Courchesne, Noémie-Manuelle Dorval; Duraj-Thatte, Anna; Praveschotinunt, Pichet; Joshi, Neel S

2018-05-01

Vast potential exists for the development of novel, engineered platforms that manipulate biology for the production of programmed advanced materials. Such systems would possess the autonomous, adaptive, and self-healing characteristics of living organisms, but would be engineered with the goal of assembling bulk materials with designer physicochemical or mechanical properties, across multiple length scales. Early efforts toward such engineered living materials (ELMs) are reviewed here, with an emphasis on engineered bacterial systems, living composite materials which integrate inorganic components, successful examples of large-scale implementation, and production methods. In addition, a conceptual exploration of the fundamental criteria of ELM technology and its future challenges is presented. Cradled within the rich intersection of synthetic biology and self-assembling materials, the development of ELM technologies allows the power of biology to be leveraged to grow complex structures and objects using a palette of bio-nanomaterials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Testing Drugs and Attesting Cures: Pharmaceutical Monopolies and Military Contracts in Eighteenth-Century France.

PubMed

Rivest, Justin

2017-01-01

This article explores the role of testing in the allocation of royal monopoly privileges for drugs in eighteenth-century France by following the multi-generational fortunes of a single "secret remedy" from 1713 to 1776: the poudre fébrifuge of the Chevalier de Guiller. On at least five occasions, this drug was tested on patients in order to decide whether it should be protected by a privilege and whether or not its vendors should be awarded lucrative contracts to supply it in bulk to the French military. Although efforts were made early in the century to test the drug through large-scale hospital trials and to relegate privilege granting to a bureaucratic commission, the case of the poudre fébrifuge instead suggests that military expediency and relatively small-scale trials administered personally by royal practitioners remained decisive in determining whether or not a drug received a monopoly privilege or a military contract.

Nanotechnology and the Treatment of HIV Infection

PubMed Central

Parboosing, Raveen; Maguire, Glenn E. M.; Govender, Patrick; Kruger, Hendrik G.

2012-01-01

Suboptimal adherence, toxicity, drug resistance and viral reservoirs make the lifelong treatment of HIV infection challenging. The emerging field of nanotechnology may play an important role in addressing these challenges by creating drugs that possess pharmacological advantages arising out of unique phenomena that occur at the “nano” scale. At these dimensions, particles have physicochemical properties that are distinct from those of bulk materials or single molecules or atoms. In this review, basic concepts and terms in nanotechnology are defined, and examples are provided of how nanopharmaceuticals such as nanocrystals, nanocapsules, nanoparticles, solid lipid nanoparticles, nanocarriers, micelles, liposomes and dendrimers have been investigated as potential anti-HIV therapies. Such drugs may, for example, be used to optimize the pharmacological characteristics of known antiretrovirals, deliver anti-HIV nucleic acids into infected cells or achieve targeted delivery of antivirals to the immune system, brain or latent reservoirs. Also, nanopharmaceuticals themselves may possess anti-HIV activity. However several hurdles remain, including toxicity, unwanted biological interactions and the difficulty and cost of large-scale synthesis of nanopharmaceuticals. PMID:22590683

Two-point correlation function in systems with van der Waals type interaction

NASA Astrophysics Data System (ADS)

Dantchev, D.

2001-09-01

The behavior of the bulk two-point correlation function G( r; T| d ) in d-dimensional system with van der Waals type interactions is investigated and its consequences on the finite-size scaling properties of the susceptibility in such finite systems with periodic boundary conditions is discussed within mean-spherical model which is an example of Ornstein and Zernike type theory. The interaction is supposed to decay at large distances r as r - (d + σ), with 2 < d < 4, 2 < σ < 4 and d + σ≤6. It is shown that G( r; T| d ) decays as r - (d - 2) for 1 ≪ r≪ξ, exponentially for ξ≪ r≪ r *, where r * = (σ - 2)ξlnξ, and again in a power law as r - (d + σ) for r≫ r *. The analytical form of the leading-order scaling function of G( r; T| d ) in any of these regimes is derived.

A unified view of convective transports by stratocumulus clouds, shallow cumulus clouds, and deep convection

NASA Technical Reports Server (NTRS)

Randall, David A.

1990-01-01

A bulk planetary boundary layer (PBL) model was developed with a simple internal vertical structure and a simple second-order closure, designed for use as a PBL parameterization in a large-scale model. The model allows the mean fields to vary with height within the PBL, and so must address the vertical profiles of the turbulent fluxes, going beyond the usual mixed-layer assumption that the fluxes of conservative variables are linear with height. This is accomplished using the same convective mass flux approach that has also been used in cumulus parameterizations. The purpose is to show that such a mass flux model can include, in a single framework, the compensating subsidence concept, downgradient mixing, and well-mixed layers.

Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal.

PubMed

Morales, Piero; Lagerwall, Jan; Vacca, Paolo; Laschat, Sabine; Scalia, Giusy

2010-05-20

Thin films of the discotic liquid crystal hexapentyloxytriphenylene (HAT5), prepared from solution via casting or spin-coating, were investigated by atomic force microscopy and polarizing optical microscopy, revealing large-scale ordered structures substantially different from those typically observed in standard samples of the same material. Thin and very long fibrils of planar-aligned liquid crystal were found, possibly formed as a result of an intermediate lyotropic nematic state arising during the solvent evaporation process. Moreover, in sufficiently thin films the crystallization seems to be suppressed, extending the uniform order of the liquid crystal phase down to room temperature. This should be compared to the bulk situation, where the same material crystallizes into a polymorphic structure at 68 °C.

The elephant in the room: collaboration and competition among relief organizations during high-profile disasters.

PubMed

Subbarao, Italo; Wynia, Matthew K; Burkle, Frederick M

2010-01-01

The non-governmental organizations (NGOs) that assume the bulk of emergency care during large-scale disasters in the developing world must expend considerable time and resources to ensure donations to sustain their field operations. This long-standing dilemma for the humanitarian community can create a competitive environment that: Compromises the delivery and quality of services, Allows the effectiveness of operations to be compromised by a lack of cooperation and collaboration, Disrupts the timely and accurate coordination and analysis of outcome measures that are crucial to successful response in the future, and Undermines the long-term capacity of indigenous aid organizations. This article addresses problems and potential solutions for improved coordination and long-term capacity-building of humanitarian aid.

Nacre-mimetic bulk lamellar composites reinforced with high aspect ratio glass flakes.

PubMed

Guner, Selen N Gurbuz; Dericioglu, Arcan F

2016-12-05

Nacre-mimetic epoxy matrix composites reinforced with readily available micron-sized high aspect ratio C-glass flakes were fabricated by a relatively simple, single-step, scalable, time, cost and man-power effective processing strategy: hot-press assisted slip casting (HASC). HASC enables the fabrication of preferentially oriented two-dimensional inorganic reinforcement-polymer matrix bulk lamellar composites with a micro-scale structure resembling the brick-and-mortar architecture of nacre. By applying the micro-scale design guideline found in nacre and optimizing the relative volume fractions of the reinforcement and the matrix as well as by anchoring the brick-and-mortar architecture, and tailoring the interface between reinforcements and the matrix via silane coupling agents, strong, stiff and tough bio-inspired nacre-mimetic bulk composites were fabricated. As a result of high shear stress transfer lengths and effective stress transfer at the interface achieved through surface functionalization of the reinforcements, fabricated bulk composites exhibited enhanced mechanical performance as compared to neat epoxy. Furthermore, governed flake pull-out mode along with a highly torturous crack path, which resulted from extensive deflection and meandering of the advancing crack around well-aligned high aspect ratio C-glass flakes, have led to high work-of-fracture values similar to nacre.